Apparatus and method for rapid start-up of short-cut nitrification process

Abstract

This invention relates to a device and method for rapidly starting a short-cut nitrification process, belonging to the field of water treatment. The invention involves inoculating a secondary sedimentation tank with sludge and adding a polyurethane biological sponge carrier into a sequencing batch reactor (SBR). First, a phased influent influent + incremental post-aeration strategy (increasing aeration time first, then increasing aeration rate) is adopted. This utilizes nitrate and a dynamic oxygen environment to drive the migration of *Candidatus Contendobacter* to the sponge carrier and complete its enrichment and acclimatization, reducing the obstruction of O2 on the endogenous denitrification process of *Candidatus Contendobacter* under aerobic conditions. The phased influent influent is then eliminated, and NH4 is introduced. + -N synthesis wastewater is treated using a low-alkalinity strategy (reducing influent KHCO3 concentration) + post-aeration with an initial increase followed by a decrease in aeration volume, combined with strong NO2 stimulation from Candidatus Contendobacter in a low dissolved oxygen environment. ‑ -N reducing power inhibits NOB growth, enabling rapid start-up of the short-cut nitration process.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to an apparatus and method for rapidly starting a short-cut nitrification process. Background Technology

[0002] Due to the high energy consumption and carbon emission limitations of traditional biological wastewater treatment processes, scholars both domestically and internationally are continuously exploring new wastewater treatment methods to improve the sustainability of wastewater treatment plants (WWTPs). Compared to the total nitrification process (NH4+), + -N→NO3 - -N), short-cut nitration (PN)(NH4) + -N→NO2 - Nitrogen oxides (NOx) have advantages such as low aeration energy consumption and ease of coupling with other processes, leading to the development of coupled nitrogen removal processes such as short-cut nitrification / denitrification, short-cut nitrification / anaerobic ammonium oxidation, and simultaneous short-cut nitrification / denitrification. These new processes generally improve nitrogen removal efficiency while reducing energy consumption. Among these, PN, as the front-end process of the above processes, requires rapid start-up and stability, which are prerequisites for efficient nitrogen removal in the coupled system.

[0003] Achieving a stable PN process requires enhancing the activity of ammonia-oxidizing bacteria (AOB) and stably inhibiting or eliminating nitrite-oxidizing bacteria (NOB), thereby achieving AOB enrichment. Therefore, rapid PN startup aims to flush NOB out of the system within a short time while effectively retaining AOB. It is known that in low ammonia nitrogen concentration (40-80 mg / L) environments in domestic wastewater, AOB has limited available ammonia nitrogen substrates, and NOB has a higher affinity for both substrates and oxygen. Therefore, how to rapidly start the PN process has become a key research direction. Recent studies have identified several factors related to PN startup, including temperature, dissolved oxygen, pH, free nitrite, and sludge age. Optimizing these factors comprehensively is crucial for starting short-cut nitrification. It has also been found that optimizing aeration methods, applying external magnetic fields, using ultrasound, or adding chemical reagents can accelerate the short-cut nitrification startup process. However, meeting some of these conditions in practical applications is challenging and costly, making it difficult to achieve. Furthermore, hydroxylamine is frequently used to promote the initiation of PN processes, but the large-scale input of chemical reagents may cause irreversible damage to other functional bacteria in the system, and long-term addition increases operating costs. Therefore, there is an urgent need to develop a novel, effective, low-cost, and non-biotoxic method for initiating PN processes.

[0004] NH4 + -N oxidation reaction is controlled at NO2 - In the -N stage, it is not further oxidized to NO3 by NOB. --N is the key and target for initiating PN. Previous studies have focused on the differences in metabolism or survival conditions between AOB and NOB, but have not addressed the competition between the two from a bio-assisted perspective. For example, utilizing denitrification to remove NO2... - -N is directly reduced to N2 without further oxidation. This may be attributed to the tendency of external organic matter to be oxidized in aerobic environments rather than being supplied to ordinary heterotrophic denitrifying bacteria for denitrification. Therefore, enhancing the denitrification activity of denitrifying bacteria in the aerobic zone has become a key breakthrough in this technical challenge. In recent years, the endogenous denitrification process carried out by denitrifying polysaccharide bacteria has attracted much attention. Under anaerobic conditions, these bacteria convert external organic matter into polyhydroxy fatty acid esters (PHAs), an internal carbon source, effectively reducing the waste of carbon sources in the aerobic zone. It is known that *Candidatus contendobacter* exhibits excellent NO2 production in a favorable environment. - -N reduction performance. Based on this, this study addresses the challenge of slow start-up speed in the PN process by developing a device and method for rapidly starting up a short-cut nitration process, which is of great significance for promoting the practical application of the PN process and achieving sustainable development. Summary of the Invention

[0005] This invention addresses the technical problem of how to achieve rapid start-up of the PN process, and provides an apparatus and method for rapidly starting up a short-cut nitration process. This invention also provides a rapid start-up apparatus for implementing this method.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0007] A method for rapidly starting a short-cut nitrification process includes: (1) inoculating a secondary sedimentation tank sludge into a sequencing batch reactor and adding a polyurethane bio-sponge carrier. A carbon source culture medium is introduced before the start of each cycle, and the system cycle duration is set to 6-8 hours. When the stirring operation reaches 1 / 4 of the reaction cycle duration, nitrate concentrate is introduced, and the NO3 content in the reactor is controlled after the nitrate concentrate is introduced. - -N concentration is 40-80 mg / L. This is determined by the C / N ratio (COD / NO3). - Adjust the COD concentration of the carbon source medium (COD supplied by CH3COONa) within the range of 2.7-3.0 (NO3-N) to regulate the system to the total nitrogen (NO3-N) level. - -N and NO2 -The total nitrogen (DO) removal rate was higher than 95%. Subsequently, a post-aeration incremental strategy (increasing duration first, then aeration rate) was adopted. Aeration began after the introduction of concentrated nitrate solution, initially controlling the dissolved oxygen (DO) concentration in the system at 0.1 mg / L and the aeration time at 1 hour. The remaining reaction cycle continued under anoxic conditions. While maintaining a total nitrogen removal rate above 95%, only the aeration time was increased, by 0.5 hours per cycle. The aeration time was stopped when the total nitrogen removal rate fell below 95%. After determining the aeration time, the aeration rate was increased incrementally per cycle, corresponding to a single increase of 0.5 mg / L in DO concentration. The critical points were set at 1-2 mg / L DO and a total nitrogen removal rate below 90%, and when high-throughput data showed *Candidatus Contendobacter* as the most abundant microbial genus in the system, the pre-culture of *Candidatus Contendobacter* was terminated. The concentration of COD in the influent and the concentration of NO3 in the nitrate concentrate after the final cycle of this step were measured. - -N concentration and DO concentration during aeration are used to determine the influent COD and NH4 concentrations for subsequent steps. + -N concentration and aeration rate during aeration. (2) Based on the Candidatus Contendobacter sludge, biological carrier, and determined cycle and aeration duration obtained in step (1), start the short-cut nitrification process. Specifically: before the device starts operating, introduce synthetic wastewater and start aeration when the stirring operation reaches 1 / 4 of the reaction cycle duration. First, increase the aeration rate once to maintain the DO concentration in the device consistent with the DO concentration measured in the last cycle of step (1). Under this condition, operate until there is no NH4 in the effluent. + -N remains and NO3 - When the NH4+ concentration is higher than 5 mg / L, the aeration rate should be gradually reduced in stages, with each reduction in DO concentration not exceeding 0.2 mg / L, until no NH4+ is detected in the effluent. + -N and NO3 - -N remains. Finally, based on the nitrogen concentration monitored by the device throughout the cycle, the aeration rate is further reduced so that NH4+ is reduced at the end of aeration. + -N is completely removed and NO3 is present throughout the entire cycle. - When the -N concentration is below 2 mg / L, the critical point is reached, at which point the reduction of aeration rate is stopped, and the short-cut nitrification process is started.

[0008] When inoculating the secondary sedimentation tank sludge in step (1), the volume of the inoculated sludge accounts for 30% to 40% of the total volume of the reactor. The total suspended solids in the initial mixed liquor formed by stirring are about 2500 to 3000 mg / L, and the concentration ratio of volatile suspended solids to total suspended solids in the initial mixed liquor is 0.4 to 0.7.

[0009] The polyurethane bio-sponge carrier monomers added in step (1) are 3cm×3cm×3cm in size, and the total volume of the added carriers is 10-15% of the reactor volume.

[0010] In step (1), the temperature inside the reactor is controlled at 25-30℃ and the pH value is 7.5-8.0.

[0011] In step (1), the carbon source culture medium and its concentration requirements are as follows: COD concentration greater than or equal to 100 mg / L (CH3COONa greater than or equal to 128.17 mg / L), KHCO3 concentration of 1000 mg / L, and also include 60 mg / L CaCl2, 60 mg / L MgSO4·7H2O and 1 ml / L trace element solution. The concentrations of each trace element in the trace element solution are as follows: EDTA, 15000 mg / L; CoCl2·6H2O, 240 mg / L; ZnSO4·7H2O, 430 mg / L; MnCl2·2H2O, 990 mg / L; NaMoO4·2H2O, 220 mg / L; CuSO4·5H2O, 250 mg / L; Na2SeO4·10H2O, 210 mg / L; NiCl2·6H2O, 190 mg / L; and H3BO3, 14 mg / L.

[0012] In step (2), the required substances and concentrations of the synthetic wastewater introduced before the start of device operation are: NH4 + The NO3- concentration is 40-80 mg / L, and it needs to be introduced into the reactor along with the concentrated nitrate solution measured in the last cycle of step (1). - -N concentration was consistent, KHCO3 concentration decreased to 700 mg / L, COD concentration was consistent in the last cycle of step (1), and also included 9 mg / L PO4. 3- -P, 60 mg / L CaCl2, 60 mg / L MgSO4·7H2O and 1 ml / L trace element solution, the substances and concentrations of the trace element solution are the same as in step (1).

[0013] A rapid start-up device for a short-cut nitrification process to implement the aforementioned method includes a sequencing batch reactor (SBR), which is equipped with a stirring device; a polyurethane bio-sponge carrier; an aeration device; an inlet tank connected to the SBR via an inlet pipe, on which an inlet pump and inlet valve are installed; a nitrate storage tank connected to the SBR via a nitrate delivery pipe, on which an inlet pump and inlet valve are installed; a drain tank connected to the SBR via a drain pipe, on which a drain valve is installed; and online monitoring and control equipment for real-time monitoring of NH4 in the reactor. + -N, NO3- -N, NO2 - -N, DO concentrations and pH values ​​can be automatically adjusted based on nitrogen concentration using the system settings of the rotor flowmeter.

[0014] The method for rapid start-up of the short-cut nitration process in this invention is based on the timely reduction of NO2 generated in the PN process. - -N can inhibit NOB growth and Candidatus Contendobacter has the ability to utilize stored PHA for denitrification in low DO environments. This provides a rapid start-up method for PN (Non-Nutrition Process) that is primarily biologically assisted, supplemented by aeration and alkalinity control, solving the problem of long start-up time in practical applications. First, secondary sedimentation tank sludge is inoculated into the SBR reactor, and a polyurethane biological sponge carrier is added. A phased influent + incremental post-aeration strategy (increasing duration first, then increasing aeration rate) is used to drive Candidatus Contendobacter to migrate to the sponge carrier and complete enrichment and acclimatization using nitrate and dynamic oxygen environments. Afterwards, the phased influent method is eliminated, and NH4+ is introduced in a single pass. + For synthetic wastewater primarily composed of nitrogen (N), a low-alkalinity strategy (reducing influent KHCO3 concentration) + post-aeration with an initial increase followed by a decrease in aeration volume is adopted, combined with the strong NO2 stimulation of Candidatus Contendobacter in a low dissolved oxygen environment. - -N's reducing ability hinders NOB growth, assists in the rapid enrichment of AOB, and thus enables the rapid start-up of the PN process.

[0015] The apparatus and method for rapidly starting up a short-path nitration process as described in this invention have the following advantages:

[0016] (1) Due to O2 and NO x - Both -N and -N can act as electron acceptors for Candidatus Contendobacter, consuming intracellularly stored PHA. Therefore, when starting the PN process with direct aeration, the pre-existing presence of O2 makes it difficult for Candidatus Contendobacter to perform endogenous denitrification in an aerobic environment, thus failing to successfully compete for NO2. - -N is used to inhibit NOB growth. This invention employs a segmented influent + incremental post-aeration strategy (in terms of duration and aeration rate) to utilize NO3-. - -N is the preferred electron acceptor for pre-culturing activated sludge, and the dynamic oxygen environment is used to drive the migration of Candidatus Contendobacter to the sponge carrier for enrichment. Candidatus Contendobacter sludge and biofilm with reduced O2 interference can be obtained within 15 days.

[0017] (2) The addition of polyurethane bio-sponge carriers provides a locally anoxic region for Candidatus Contendobacter in an aerobic environment, which is more conducive to the denitrification process of Candidatus Contendobacter. Therefore, preferentially driving the accumulation of Candidatus Contendobacter in the sponge carrier can further promote the capture of NO2 by Candidatus Contendobacter. - -N.

[0018] (3) Even after pre-culture, Candidatus Contendobacter still primarily produced NO in environments with low dissolved oxygen levels. x - -N is the dominant electron acceptor. Compared to NOB whose activity has not yet recovered, AOB produces NO2 under low DO conditions. - -N is initially reduced by Candidatus Contendobacter, causing NOB to be eliminated due to lack of substrate, thus creating favorable conditions for AOB growth. The PN process can be initiated within 10 days based on the obtained Candidatus Contendobacter sludge and biofilm.

[0019] (4) In addition to the main auxiliary role of Candidatus Contendobacter, multiple aeration and low alkalinity strategies further accelerate the start-up of the PN process. In the early stage, the interference of O2 on Candidatus Contendobacter is reduced by the strategy of increasing post-aeration (first increasing the duration, then increasing the aeration rate). In the later stage, the low alkalinity (reducing the influent KHCO3 concentration) + post-aeration (increasing and then decreasing the aeration rate) strategy creates a low substrate and low dissolved oxygen environment to reduce the available inorganic carbon source of NOB and O2, and promote the enrichment of AOB.

[0020] (5) Compared with the traditional method of starting the PN process, the starting method provided by this invention, which is mainly assisted by Candidatus Contendobacter and supplemented by aeration and alkalinity control, can save the cost of long-term chemical reagent addition and has the characteristics of high efficiency, stability and no biological toxicity.

[0021] To make the technical solution of the apparatus and method for rapid start-up of short-cut nitration process of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0022] like Figure 1 The diagram shown is a schematic of the rapid start-up device for the short-path nitration process described in this invention.

[0023] The attached figures are labeled as follows:

[0024] 1-SBR reactor; 11-Stirring device; 12-Aeration disc; 13-Rotameter; 14-Air pump; 15-Polyurethane biological sponge carrier; 2-Inlet tank; 3-Nitrate storage tank; 4-Outlet tank; 5-Online monitoring and control equipment; 6-Carbon source inlet pump; 7-Inlet pump. Detailed Implementation

[0025] The present invention will be further described below with reference to specific implementation examples, but the scope of protection of the present invention is not limited thereto.

[0026] Example 1

[0027] This embodiment provides a rapid start-up device for a short-range nitration process, the structure of which is as follows: Figure 1 As shown, the reactor includes an SBR reactor 1 with a working volume of 5L, equipped with a stirring device 11 and an aeration disc 12. An air pump 14 is connected to the aeration disc via a rotor flow meter 13. A polyurethane biological sponge carrier 15 is added to the reactor. The inlet tank includes an inlet tank 2 and a nitrate storage tank 3, which are connected to an inlet pump 6 and a nitrate inlet pump 7, respectively. The outlet tank 4 is used to store the reactor effluent. The sensors of the online monitoring and control device 5 are installed inside the SBR reactor to monitor the NH4+ in the reactor during operation. + -N, NO3 - -N, NO2 - Real-time monitoring of -N, DO concentrations and pH values, and automatic adjustment of the rotor flowmeter 13 based on nitrogen concentration through system settings.

[0028] When the device is started, two types of feed water are prepared using deionized water for the pre-culture of Candidatus Contendobacter. Feed water 1 (carbon source medium) contains 138-150 mg / L CH3COONa (108-117 mg / L COD), 60 mg / L CaCl2, 60 mg / L MgSO4·7H2O, 1000 mg / L KHCO3, and 1 ml / L trace element solution. The pH of the feed water is maintained between 7.5 and 8.0. It is placed in feed water tank 2. Before the start of each cycle in step (1), 2.5 L of carbon source medium is pumped into the reactor using feed water pump 7. Feed water 2 (nitrate concentrate) contains 10000 mg / L NO3. - -N is placed in nitrate storage tank 3. When the reaction cycle is 1 / 4 complete, 10 mL of concentrated nitrate solution is pumped into the device via inlet pump 6. After pumping in, NO3 in the device... --N concentration is 40 mg / L. The standard determination steps (1) include the COD concentration in the influent (117 mg / L) and the NO3 concentration in the device after the nitrate concentrate is introduced. - -N concentration (40 mg / L) was used to prepare an influent for the PN process start-up using deionized water. The composition and concentration of influent 3 were: 117 mg / L COD (150 mg / L CH3COONa), 40 mg / L NH4+. + -N, 9 mg / L PO4 3- A solution of -P, 60 mg / L CaCl2, 60 mg / L MgSO4·7H2O, 700 mg / L KHCO3, and 1 ml / L trace elements was placed in the influent tank 2, with the pH of the influent maintained between 7.5 and 8.0. Before the start of each cycle in step (2), 2.5 L of influent 3 was pumped into the reactor using the influent pump 7. After the single cycle was completed and the sludge sedimentation was finished, the 2.5 L of solution in the reactor was discharged into the effluent tank 4.

[0029] The concentrations of each trace element in the trace element solution are as follows: EDTA, 15000 mg / L; CoCl2·6H2O, 240 mg / L; ZnSO4·7H2O, 430 mg / L; MnCl2·2H2O, 990 mg / L; NaMoO4·2H2O, 220 mg / L; CuSO4·5H2O, 250 mg / L; Na2SeO4·10H2O, 210 mg / L; NiCl2·6H2O, 190 mg / L; and H3BO3, 14 mg / L.

[0030] The method for rapidly starting up the short-path nitration process described in this embodiment includes the following specific steps:

[0031] (1) Secondary sedimentation tank sludge was used as inoculum in the SBR reactor. The volume of the inoculum sludge accounted for 30% of the total volume of the SBR reactor. After stirring the influent, the total suspended solids in the initial mixed liquor were 2500 mg / L, and the ratio of volatile suspended solids to total suspended solids in the initial mixed liquor was 0.5. Twenty polyurethane bio-sponge carriers with a size of 3cm×3cm×3cm were added, and the total volume of the added carriers was about 10% of the reactor volume. The SBR reactor was set with a effluent ratio of 50%, an operating cycle of 6 hours, and 2 cycles per day.

[0032] Before the start of each cycle, 2.5L of influent 1 is introduced, initially setting the C / N ratio to 2.7. When the reaction cycle reaches 1 / 4 of its duration (1.5 hours), 10mL of influent 2 is introduced. After the introduction of influent 2, NO3 in the reactor... -The nitrogen concentration was 40 mg / L. During operation, the concentration of CH3COONa in influent 1 was increased periodically until the total nitrogen removal rate exceeded 95%. On day 5, when the C / N ratio was 2.9, the total nitrogen removal rate increased to 96.45%. Subsequently, on day 6, a post-aeration incremental strategy (increasing duration first, then aeration volume) was adopted. Aeration began after the introduction of influent 2, and the DO concentration in the reactor was controlled at 0.1 mg / L, with an aeration time of 1 h. While the total nitrogen removal rate was above 95%, the aeration time was increased by 0.5 h per cycle, stopping when the total nitrogen removal rate fell below 95%. On day 7, the total nitrogen removal rate decreased to 94.50%, and the aeration time was stopped. At this point, the aeration time per cycle was 2.5 hours, and the remaining 2 hours of the reaction cycle were operated in an anoxic state. After determining the aeration duration, the aeration rate was gradually increased in cycles, corresponding to a single increase of 0.5 mg / L in dissolved oxygen within the device, with 1-2 mg / L DO and a total nitrogen removal rate below 90% as the critical points. On the 10th day, the total nitrogen removal rate was 92.7%. High-throughput testing results showed that the relative abundance of *Candidatus Contendobacter* in flocculent sludge was 28.25%, and its relative abundance in biofilm was 37.65%, making it the most abundant species in both sludge and biofilm, thus completing the pre-cultivation step of *Candidatus Contendobacter*. Measurements were taken of the COD concentration in the influent during the final cycle and the NO3 concentration in the device after the nitrate concentrate was introduced. - -N concentrations were 117 mg / L and 40 mg / L, respectively, and DO concentration in the device was 1.1 mg / L during aeration. In this embodiment, the specific final process and water intake process of this stage are as follows: at the beginning of operation, water intake 1 is introduced, followed by a stirring process; after stirring for 1.5 hours, water intake 2 is introduced for 1 minute, followed by a 2.5-hour aeration and stirring process; the last 2 hours are run with only stirring.

[0033] (2) Based on the Candidatus Contendobacter sludge and biofilm in step (1), cancel the introduction of influent 1 and 2, and introduce 2.5L of influent 3 before the start of each cycle. The COD concentration of the influent is the same as that in the last cycle of step (1) (117mg / L), and the NH4+ concentration is... + -N concentration and NO3 in the device after the last cycle of nitrate concentrate is introduced. --N concentration was consistent (40 mg / L). The specific process and water intake process were as follows: water 3 was introduced at the beginning of operation, followed by a 1.5-hour stirring process; then a 2.5-hour aeration and stirring process; and finally, stirring only for the last 2 hours. An online monitoring and control device program was set up to increase the aeration rate once during the 2.5-hour aeration period until the DO concentration in the reactor was consistent with the DO concentration measured in the last cycle of step (1) (1.1 mg / L); after the reaction was completed on the 15th day, the effluent did not contain NH4. + -N, nitrifying bacteria are activated, but NO3 in the effluent - The -N concentration was 6 mg / L. Aeration was gradually reduced in stages, with each reduction in DO concentration not exceeding 0.2 mg / L. On day 18, the effluent NH4... + -N and NO3 - -N concentrations were all 0 mg / L, NO2 - The -N concentration was 5.76 mg / L, and the DO concentration in the reactor during aeration was 0.5 mg / L. Online monitoring and control equipment indicated the presence of NO3- during operation. - With NH4+ concentrations exceeding 2 mg / L, the aeration rate was gradually reduced. On day 20, the DO concentration in the reactor during aeration was below 0.2 mg / L. Real-time monitoring showed that no NH4+ was detected in the water at the end of aeration. + -N remains and NO3 runs throughout. - -N concentration below 2 mg / L indicates successful start-up of the PN process. High-throughput testing results showed that the relative abundance of *Nitrosomonas* (AOB) was 3.71 times that of *Nitrospira* (NOB), further confirming the successful start-up of the PN process.

[0034] The total start-up time for this embodiment was 20 days, including 10 days of pre-culture of Candidatus Contendobacter and 10 days of PN process start-up. Monitoring showed that after 30 days of operation, the PN process was running stably, and no NH4 was found in the water at the end of aeration. + -N remains, NO3 is present throughout reactor operation. - -N concentration remained below 2 mg / L and AOB continued to accumulate.

[0035] Example 2

[0036] The short-range nitration process rapid start-up device in this embodiment is the same as in Embodiment 1.

[0037] When the device is started, two types of feed water are prepared using deionized water for the pre-culture of Candidatus Contendobacter. Feed water 1 (carbon source medium) contains 277-308 mg / L CH3COONa (216-240 mg / L COD), 60 mg / L CaCl2, 60 mg / L MgSO4·7H2O, 1000 mg / L KHCO3, and 1 ml / L trace element solution. The pH of the feed water is maintained between 7.5 and 8.0. It is placed in feed water tank 2. Before the start of each cycle in step (1), 2.5 L of carbon source medium is pumped into the reactor using feed water pump 7. Feed water 2 (nitrate concentrate) contains 20000 mg / L NO3. - -N is placed in nitrate storage tank 3. When the reaction cycle is 1 / 4 complete, 10 mL of concentrated nitrate solution is pumped into the reactor through inlet pump 6. After pumping in, NO3 in the device... - -N concentration is 80 mg / L. The standard determination steps (1) include the COD concentration (240 mg / L) in the influent during the last cycle, and the NO3 concentration in the device after the nitrate concentrate is introduced. - -N concentration (80 mg / L), a feed water solution was prepared using deionized water for PN process start-up. The feed water solution 3, prepared using deionized water for PN process start-up, had the following composition and concentration: 308 mg / L CH3COONa (240 mg / L LCOD), 80 mg / L NH4+. + -N, 9 mg / L PO4 3- A solution of -P, 60 mg / L CaCl2, 60 mg / L MgSO4·7H2O, 700 mg / L KHCO3, and 1 ml / L of trace elements is placed in the influent tank 2, with the pH of the influent maintained between 7.5 and 8.0. Before the start of each cycle in step (2), 2.5 L of influent 3 is pumped into the reactor using the influent pump 7. After the single cycle is completed and the sludge sedimentation is finished, the 2.5 L of solution in the reactor is discharged into the effluent tank 4.

[0038] The composition of the trace element solution is the same as that in Example 1.

[0039] The method for rapidly starting up the short-path nitration process described in this embodiment includes the following specific steps:

[0040] (1) Secondary sedimentation tank sludge was used as inoculum in the SBR reactor. The volume of the inoculum sludge accounted for 30% of the total volume of the SBR reactor. After mixing the influent, the total suspended solids in the initial mixed liquor were 2800 mg / L, and the ratio of volatile suspended solids to total suspended solids in the initial mixed liquor was 0.5. Twenty-five polyurethane bio-sponge carriers with a size of 3cm×3cm×3cm were added, and the total volume of the added carriers was approximately 13.5% of the reactor volume. The SBR reactor was set with a effluent ratio of 50%, an operating cycle of 8 hours, and two cycles per day.

[0041] Before the start of each cycle, 2.5L of influent 1 is introduced, initially setting the C / N ratio to 2.7. When the reaction cycle is 1 / 4 complete (2 hours), 10mL of influent 2 is introduced. After the introduction of influent 2, NO3 in the reactor... - -N concentration was 80 mg / L; during operation, the CH3COONa concentration in influent 1 was increased periodically until the total nitrogen removal rate was higher than 95%; on the 6th day, when the C / N ratio was 3.0, the total nitrogen removal rate increased to 98.21%; then on the 7th day, a post-aeration incremental strategy (increasing the duration first, then increasing the aeration volume) was adopted, and aeration was started after influent 2 was introduced, controlling the DO concentration in the reactor to be 0.1 mg / L and the aeration time to be 1 h. With the total nitrogen removal rate (TN) above 95%, the aeration time was increased by 0.5 hours per cycle, stopping when the TN removal rate fell below 95%. On day 9, the TN removal rate decreased to 93.75%, and the aeration time was stopped. At this point, the aeration time per cycle was 3 hours, and the remaining 3 hours of the reaction cycle were operated in an anoxic state. After determining the aeration time, the aeration volume was increased incrementally per cycle, corresponding to a single increase of 0.5 mg / L in DO within the device. On day 11, the TN removal rate was 91.34%. High-throughput testing showed that the relative abundance of Candidatus Contendobacter in the flocculent sludge was 26.85%, and the relative abundance in the biofilm was 35.27%, making it the most abundant species in both sludge and biofilm, thus completing the Candidatus Contendobacter pre-cultivation step. Measurements were taken of the COD concentration in the influent and the NO3 concentration in the device after the nitrate concentrate was introduced in the last cycle. - -N concentrations were 240 mg / L and 80 mg / L, respectively, and DO concentration in the device was 1.6 mg / L during aeration. In this embodiment, the final specific process and water intake process of this stage are as follows: at the beginning of operation, water intake 1 is introduced, followed by a stirring process; after stirring for 2 hours, water intake 2 is introduced for 1 minute, and after water intake 2 is introduced, a 3-hour aeration and stirring process is carried out; the last 3 hours are run with only stirring.

[0042] (2) Based on the Candidatus Contendobacter sludge and biofilm in step (1), cancel the introduction of influent 1 and 2, and introduce 2.5L of influent 3 before the start of each cycle. The COD concentration of the influent is the same as that in the last cycle of step (1) (240mg / L), NH4 + -N concentration and NO3 in the device after the last cycle of nitrate concentrate is introduced. - -N concentration was consistent (80 mg / L). The specific process and water intake process were as follows: water 3 was introduced at the beginning of operation, followed by a 2-hour stirring process; then a 3-hour aeration and stirring process; and finally, a 3-hour stirring-only operation. An online monitoring and control device program was set up to increase the aeration rate once during the 3-hour aeration period until the DO concentration in the reactor was consistent with the DO concentration measured in the last cycle of step (1) (1.6 mg / L); after the reaction was completed on the 16th day, the effluent did not contain NH4. + -N, nitrifying bacteria are activated, but NO3 in the effluent - The -N concentration was 6.5 mg / L. Aeration was gradually reduced in stages, with each reduction in DO concentration not exceeding 0.2 mg / L. On day 17, the effluent NH4... + -N and NO3 - -N concentrations were all 0 mg / L, NO2 - The -N concentration was 6.94 mg / L, and the DO concentration in the reactor during aeration was 0.4 mg / L; the online monitoring and control equipment showed the presence of NO3 during operation. - With NH4+ concentrations exceeding 2 mg / L, the aeration rate was gradually reduced. On day 19, the DO concentration in the reactor during aeration was below 0.15 mg / L. Real-time monitoring showed that no NH4+ was detected in the water at the end of aeration. + -N remains and NO3 runs throughout. - -N concentration below 2 mg / L indicates successful start-up of the PN process. High-throughput testing results showed that the relative abundance of *Nitrosomonas* (AOB) was 4.08 times that of *Nitrospira* (NOB), further confirming the successful start-up of the PN process.

[0043] The total start-up time for this embodiment was 19 days, including 11 days of pre-culture of Candidatus Contendobacter and 8 days of PN process start-up. Monitoring showed that after 30 days of operation, the PN process was running stably, and no NH4 was found in the water at the end of aeration. + -N remains, NO3 is present throughout reactor operation. - -N concentration remained below 2 mg / L and AOB continued to accumulate.

[0044] Comparative Example

[0045] This comparative example was conducted simultaneously with the experiment in Example 1, but the experimental setup differed. The main difference was that Candidatus Contendobacter was not pre-cultured; instead, the PN process was started directly using a low-alkalinity + post-aeration strategy with a gradual increase followed by a decrease in aeration rate. The specific start-up method in the comparative example is as follows:

[0046] (1) Inoculate the secondary sedimentation tank sludge into a 5L SBR reactor to make the total suspended solids in the reactor 2500mg / L, and the initial volatile suspended solids / total suspended solids ratio in the mixed liquor 0.5. Add 20 polyurethane bio-sponge carriers with a size of 3cm×3cm×3cm, the total volume of the carriers being about 10% of the reactor volume.

[0047] (2) At the beginning of operation, 2.5L of CH3COONa at 150mg / L and NH4 at 40mg / L are introduced. + -N, 9mg / LPO4 3- The synthetic wastewater was composed of P, 60 mg / L CaCl2, 60 mg / L MgSO4·7H2O, 700 mg / L KHCO3 and 1 ml / L trace element solution. Then, a stirring process was carried out. After stirring for 1.5 hours, an aeration and stirring process was carried out for 2.5 hours. Finally, aeration was stopped and stirring was carried out for 2 hours.

[0048] (3) Set up an online monitoring and control device program to increase the aeration rate to 1.1 mg / L in the reactor during the 2.5-hour aeration period; on the 4th day of reactor operation, nitrification began to appear during aeration, and the effluent NO2 - -N concentration is 0 mg / L, NH4 + -N concentration was 6.74 mg / L, NO3 - The -N concentration was 13.06 mg / L. Meanwhile, there was almost no reduction in total nitrogen during aeration, indicating that the Candidatus Contendobacter did not undergo endogenous denitrification during this period. By day 9, nitrification was significant, and the effluent contained no NH4+. + -N remainder, containing 10.5 mg / L NO3. - -N and 1.8 mg / L NO2 - -N, Candidatus Contendobacter's contribution to nitrogen removal during aeration remains weak, with denitrification mainly occurring during the final two hours of stirring. The aeration rate was gradually reduced in an attempt to initiate the PN process. After 19 days of reactor operation, the aeration level reached a point where NH4+ could not be removed by AOB and NOB after the aeration process was completed. + The critical point for complete removal of NO3- is reached when the dissolved oxygen concentration in the system is below 0.2 mg / L. At this point, the remaining NO3- after the aeration process... -The -N concentration (13.2 mg / L) was still higher than that of NO2. - -N (6.9 mg / L), PN process start-up failed. Later, the influent CH3COONa concentration was increased (200 mg / L) in an attempt to increase the organic matter supply and allow Candidatus Contendobacter to store more internal carbon sources, thereby driving its denitrification function during aeration. However, the effect was not significant, removing only 2 mg / L of total nitrogen. Ultimately, the formation of the polyurethane bio-sponge carrier biofilm was not obvious. High-throughput sequencing results showed that the relative abundance of Candidatus Contendobacter in the sludge was only 5.23%, and the relative abundance of Nitrosomonas (AOB) was 0.21 times that of Nitrospira (NOB). In summary, compared to the comparative example, the method for rapid start-up of the short-cut nitrification process in this invention can significantly shorten the PN process start-up time.

[0049] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the claims.

Claims

1. A method for rapidly starting a short-cut nitration process, characterized in that, include: (1) Inoculate the secondary sedimentation tank sludge into the sequencing batch reactor and add polyurethane biological sponge carrier. Before the start of each cycle, introduce the carbon source culture medium. The system cycle duration is set to 6-8 hours. When the stirring operation reaches 1 / 4 of the reaction cycle duration, introduce concentrated nitrate solution, controlling the NO3 content in the device after the introduction of concentrated nitrate solution. - -N concentration was 40-80 mg / L; the COD concentration of the carbon source medium was adjusted within the range of C / N ratio of 2.7-3.0, with COD supplied by CH3COONa, and the system was operated until the total nitrogen removal rate was higher than 95%. Subsequently, a post-aeration incremental strategy was adopted, i.e., increasing the aeration time first, then increasing the aeration volume. Aeration began after the nitrate concentrate was introduced, initially controlling the dissolved oxygen (DO) concentration in the system at 0.1 mg / L and the aeration time at 1 hour. The remaining reaction cycle continued under anoxic conditions. Only the aeration time was increased by 0.5 hours per cycle, based on a total nitrogen removal rate exceeding 95%. The aeration time was stopped when the total nitrogen removal rate fell below 95%. After determining the aeration time, the aeration volume was increased incrementally per cycle, corresponding to a single increase of 0.5 mg / L in DO concentration. The critical points were 1-2 mg / L DO and a total nitrogen removal rate below 90%, and when high-throughput data showed Candidatus Contendobacter as the most abundant microbial genus in the system, the Candidatus Contendobacter pre-culture was terminated. The COD concentration in the influent and the NO3 concentration in the device after the introduction of the nitrate concentrate were measured in the last cycle of this step. - -N concentration and DO concentration during aeration are used to determine the influent COD and NH4 concentrations for subsequent steps. + -N concentration and aeration rate during aeration; (2) Based on the Candidatus Contendobacter sludge, biological carrier, and determined cycle and aeration duration obtained in step (1), start the short-cut nitrification process; specifically: before the device starts operation, introduce synthetic wastewater, and start aeration when the stirring operation reaches 1 / 4 of the reaction cycle duration; first, increase the aeration rate once to maintain the DO concentration in the device consistent with the DO concentration measured in the last cycle of step (1); under this condition, operate until there is no NH4 in the effluent. + -N remains and NO3 - When the NH4+ concentration is higher than 5 mg / L, the aeration rate should be gradually reduced in stages, with each reduction in DO concentration not exceeding 0.2 mg / L, until no NH4+ is detected in the effluent. + -N and NO3 - -N remains; finally, based on the nitrogen concentration monitored by the device throughout the cycle, the aeration rate is further reduced so that NH4+ is reduced at the end of aeration. + -N is completely removed and NO3 is present throughout the entire cycle. - When the -N concentration is below 2 mg / L, the critical point is reached, at which point the reduction of aeration rate is stopped, and the short-cut nitrification process is started.

2. The method for rapidly starting a short-cut nitration process according to claim 1, characterized in that, When inoculating the secondary sedimentation tank sludge in step (1), the volume of the inoculated sludge accounts for 30% to 40% of the total volume of the reactor. The total suspended solids concentration in the initial mixed liquor formed by stirring is 2500 to 3000 mg / L, and the ratio of volatile suspended solids to total suspended solids concentration in the initial mixed liquor is 0.4 to 0.

7.

3. The method for rapidly starting a short-cut nitration process according to claim 1, characterized in that, The polyurethane bio-sponge carrier monomer added in step (1) is 3cm×3cm×3cm in size, and the total volume of the added carrier is 10-15% of the reactor volume.

4. The method for rapidly starting a short-cut nitration process according to claim 1, characterized in that, In step (1), the temperature inside the reactor is controlled at 25-30℃ and the pH value is 7.5-8.

0.

5. The method for rapidly starting a short-cut nitration process according to claim 1, characterized in that, In step (1), the carbon source culture medium and its concentration requirements are as follows: COD concentration greater than or equal to 100 mg / L, KHCO3 concentration of 1000 mg / L, and also includes 60 mg / L CaCl2, 60 mg / L MgSO4·7H2O and 1 ml / L trace element solution; wherein the concentrations of each trace element in the trace element solution are as follows: EDTA, 15000 mg / L; CoCl2·6H2O, 240 mg / L; ZnSO4·7H2O, 430 mg / L; MnCl2·2H2O, 990 mg / L; NaMoO4·2H2O, 220 mg / L; CuSO4·5H2O, 250 mg / L; Na2SeO4·10H2O, 210 mg / L; NiCl2·6H2O, 190 mg / L and H3BO3, 14 mg / L; In step (2), the required substances and concentrations of the synthetic wastewater introduced before the start of device operation are: NH4 + The NO3- concentration is 40-80 mg / L, and it needs to be introduced into the reactor along with the concentrated nitrate solution measured in the last cycle of step (1). - -N concentration was consistent, KHCO3 concentration decreased to 700 mg / L, COD concentration was consistent in the last cycle of step (1), and also included 9 mg / L PO4. 3- -P, 60 mg / L CaCl2, 60 mg / L MgSO4·7H2O and 1 ml / L trace element solution.

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