64 results about "Nitrate nitrogen" patented technology

The application discloses a high-salt-resistant denitrifying bacterial strain and a microsphere preparation thereof, a preparation method and application thereof, relates to the technical field of environmental microorganisms and wastewater biological treatment. Pseudomonas sp. The classification name of the strain is Pseudomonas sp., the preservation number is CGMCC No. 36626, the strain is preserved in the China General Microbiological Culture Collection Center, and the preservation date is November 14, 2025. The preparation method of the microsphere preparation containing the strain comprises the following steps: carrying out strain amplification culture to obtain a bacterial liquid, mixing the bacterial liquid with porous starch and a protective agent, then performing vacuum freeze drying to obtain bacterial powder, and then mixing the bacterial powder with a sodium alginate solution, and dropping the mixture into a calcium chloride solution to obtain the microsphere preparation. The microsphere preparation can maintain a nitrate nitrogen removal rate of more than 80% after being stored at-18 to-22 DEG C or 20 to 25 DEG C for 28 days, and can be used for denitrification and nitrogen removal of low-carbon-nitrogen-ratio and high-salt wastewater (such as urine wastewater in a closed circulation system).

This invention discloses a start-up method for a sulfur autotrophic activated sludge process, comprising: inoculation of activated sludge; internal circulation of activated sludge; a first stage of sulfur autotrophic denitrification acclimatization, wherein the supernatant recirculation ratio of the first stage is ≥400%, and the influent flow rate of nitrate nitrogen wastewater is ≤40% of the design flow rate; a second stage of sulfur autotrophic denitrification acclimatization, wherein the supernatant recirculation ratio of the second stage is greater than or equal to the supernatant recirculation ratio of the first stage; and a third stage of sulfur autotrophic denitrification acclimatization, wherein the supernatant recirculation ratio of the third stage is greater than or equal to the supernatant recirculation ratio of the second stage. The start-up procedure ends after the effluent nitrate nitrogen removal rate reaches the required level. According to the method of this invention, by combining a high proportion of recirculation with low load and low influent nitrate nitrogen wastewater, sufficient agitation of the sludge can be achieved, improving the proliferation rate of sulfur autotrophic denitrifying microorganisms while avoiding sludge loss, thus enabling rapid start-up in UASB denitrification denitrification units with a small to medium aspect ratio.

This invention discloses the application of a salt-tolerant immobilized denitrifying microbial agent in denitrification of low-temperature saline river water. The salt-tolerant immobilized denitrifying microbial agent is placed in a net bag and evenly suspended in the river channel. The salt-tolerant immobilized denitrifying microbial agent uses zeolite as the immobilization carrier, and the immobilized microorganisms are salt-tolerant denitrifying microbial agents enriched and screened from rivers flowing into the sea. The dosage of the salt-tolerant immobilized denitrifying microbial agent is 2 g·L⁻¹. ‑1 The dosage is the mass-to-volume ratio of the immobilized denitrifying bacterial agent to the river water. The low-temperature saline river water is saline river water with nitrate nitrogen as the main pollutant. The temperature of the low-temperature saline river water is 10℃~25℃. During the denitrification process, a carbon source is added to the river water to maintain denitrification efficiency. This invention has demonstrated its feasibility in practical engineering applications through pilot-scale experiments. It can effectively remediate river pollution and solve the problem of severe and difficult-to-remediate water pollution in saline rivers.

This invention belongs to the field of fertilizer additive technology, specifically relating to a Cu-containing additive. Ⅱ The coordination polymers, preparation methods, and applications are described. The preparation methods include: synthesizing N,N'-bis(3-pyridinecarboxamide)-1,2-ethane using nicotinic acid and 1,2-ethylenediamine as raw materials; and synthesizing Cu-containing polymers from N,N'-bis(3-pyridinecarboxamide)-1,2-ethane, CuCl2·2H2O, and 1,4-cyclohexane using a hydrothermal method. Ⅱ The coordination polymer [Cu(1,4-chdc)(3-dpye)]·3H2O is a blue crystal. The product prepared in this invention is used as a fertilizer additive in urea to reduce the conversion of urea N to ammonium nitrogen and ammonium nitrogen to nitrate nitrogen during urea application, thereby reducing the volatilization of NH3 into the air after urea application and the subsequent volatilization of N2O.

This application relates to the field of polymer materials, specifically disclosing a resin for removing nitrate nitrogen from high-concentration sulfate solutions and its preparation method. The preparation method includes the following steps: S1, dispersing an oil-phase solution containing styrene, divinylbenzene, a porogen, and an initiator in an aqueous solution, polymerizing, and then washing with a solvent to obtain porous polymer spheres; S2, subjecting the obtained porous polymer spheres to chloromethyl ether for chloromethylation treatment to obtain a pre-modified resin; S3, subjecting the pre-modified resin to an amination reaction with an amination reagent to obtain a nitrate-removed resin; the nitrate-removed resin has a pore size of 2-10 nm accounting for 50-90%; this application also discloses the nitrate-removed resin prepared by the above preparation method. This application has the characteristic of achieving the removal of nitrate nitrogen from high-concentration sulfate wastewater.

To enable more accurate measurement of nitrate nitrogen concentration in plants through non-destructive inspection.SOLUTION: A nitrate nitrogen concentration measurement method provided herein comprises irradiating a leaf blade 100 of a plant with first ultraviolet light L1 of a wavelength in a range of 280-320 nm to measure the amount of light transmitting through the leaf blade 100, and then calculating nitrate nitrogen concentration in the leaf blade 100 based on the amount of the transmitted first ultraviolet light L1.SELECTED DRAWING: Figure 2

The application discloses a carbon source adding amount adjusting method, device, product and medium of a denitrification process, and relates to the technical field of sewage treatment. In the method, real-time operation parameters in the denitrification process and a reaction tank volume of a reaction tank where the denitrification process is located are acquired, the real-time operation parameters including an influent flow, an influent nitrate nitrogen concentration, a terminal nitrate nitrogen concentration and a mixed liquid suspended solid concentration; a sludge denitrification rate representing current denitrification microbial activity is obtained based on the real-time operation parameters and the reaction tank volume; an influent load is determined based on the influent flow and the influent nitrate nitrogen concentration; a carbon source reference adding amount is determined according to the sludge denitrification rate and the influent load; a carbon source feedback adjusting amount is obtained according to a deviation between the terminal nitrate nitrogen concentration and a preset nitrate nitrogen target value, and the carbon source reference adding amount is corrected based on the carbon source feedback adjusting amount to obtain the carbon source adding amount. The method has the effect of ensuring accurate matching of the carbon source adding amount and actual demand.

This invention discloses a nitrogen-potassium synergistic fertilization method suitable for alfalfa cultivation in saline-alkali land, belonging to the field of agricultural fertilization technology. Addressing the problem that existing technologies lack specific alfalfa fertilization methods for saline-alkali land and fail to stimulate nitrogen fixation by rhizobia through nutrient synergy, resulting in high nitrogen fertilizer dependence and low utilization, the invention includes: measuring the rhizosphere soil electrical conductivity before sowing or before the greening stage to classify the degree of saline-alkali stress, and measuring the nitrate nitrogen content; dynamically adjusting the mass ratio of nitrogen to potassium oxide in the fertilizer based on the nitrate nitrogen content and salinity level; selecting a baseline ratio based on the salinity level when soil nitrate nitrogen is low, halving nitrogen application when moderate, and stopping nitrogen fertilizer application when sufficient; applying exogenous nitrogen fertilizer twice during the greening to initial flowering stage, and applying potassium fertilizer containing potassium humate once during the greening to branching stage, with the potassium humate supplying no less than 30% of the total potassium. This method is mainly used for alfalfa cultivation in saline-alkali land, achieving efficient synergistic utilization of nitrogen and potassium and alleviating saline-alkali stress.

The application provides a device and method for treating high-salt and high-ammonia-nitrogen wastewater by adopting hydrogen-free electrochemistry, the device comprises an electrolysis circulation unit, an oxygen cathode hydrogen-free alkali production unit and a waste gas absorption and recycling unit; the electrolysis circulation unit is communicated with or cut off from one end of the oxygen cathode hydrogen-free alkali production unit and the waste gas absorption and recycling unit, and the electrolysis circulation unit is communicated with a standby alkali tank and the other end of the waste gas absorption and recycling unit respectively; by the device and method for treating high-salt and high-ammonia-nitrogen wastewater by adopting hydrogen-free electrochemistry, the structure of the device can be optimized, pH self-maintenance, hydrogen-free safe electrolysis, alkali liquor self-production and self-use, absorption liquid resourceization can be realized, there is no secondary pollution in the treatment process, the problems of large pH fluctuation, many by-products of nitrate nitrogen, prominent safety hazards and high operation cost in the traditional process are effectively solved, and safety, energy saving and low cost are provided for high-salt and high-ammonia-nitrogen wastewater treatment.

The application discloses a light-controlled oxidation-reduction dual-mode biochar and application of the biochar in construction of a self-purification biological buffer zone, and belongs to the field of environmental functional materials and agricultural non-point source pollution control technology. The application takes biomass resource utilization as a channel, and prepares a light-controlled oxidation-reduction dual-mode biochar by co-pyrolysis of a semiconductor material precursor and biomass rich in nitrogen / sulfur through a one-step pyrolysis method. The prepared biochar utilizes photo-generated holes to oxidize and degrade organic pollutants and nitrate ammonia nitrogen into nitrate nitrogen under daytime light, and stores photo-generated electrons in doped sites of the biochar skeleton at the same time. The stored electrons are released to reduce nitrate nitrogen into nitrogen in situ at night. The dual-mode biochar is used as a core functional filler to construct a self-purification biological buffer zone, and efficient and synergistic removal of nitrogen and phosphorus pollutants and pesticides is realized by utilizing natural day and night alternation, and the buffer zone is endowed with continuous self-purification capacity, so that the risk of saturation of traditional fillers and secondary pollution is solved.

This invention provides a wastewater denitrification control system and method based on dynamic anoxic quality control. The system is implemented based on AAO (Anoxic Aseptic) and its modified processes, and includes: a data acquisition unit for real-time acquisition of parameters such as influent flow rate, influent ammonia nitrogen concentration, influent Kjeldahl nitrogen concentration, sludge return flow rate, internal circulation return flow rate, and ammonia nitrogen and nitrate nitrogen concentrations at the end of the pre-anoxic tank; a data processing unit for receiving the parameter information acquired by the data acquisition unit, processing the data to obtain the current operating status, and generating control commands based on the current operating status; and a control unit for receiving the control commands sent by the data processing unit and controlling the actions of each actuator in the biological unit according to the corresponding control commands, adjusting the operating parameters of the biological unit. This invention successfully solves the time delay problem of traditional control decisions, fills the gap in traditional control strategies regarding denitrification control, and can treat domestic wastewater in a timely and efficient manner.

This invention provides a combined heterotrophic and autotrophic denitrification treatment device, relating to the field of water treatment technology. It includes a pretreatment unit, a heterotrophic denitrification unit, an autotrophic denitrification unit, and a deep filtration unit connected in sequence. The device employs a combined process of heterotrophic denitrification for preliminary nitrogen removal and autotrophic denitrification for deep nitrogen removal. First, heterotrophic denitrification rapidly removes most of the nitrate, reducing the influent load. Then, sulfur-based autotrophic denitrification achieves deep nitrogen removal. This method is adaptable to various wastewaters with high and low C / N ratios, resulting in more thorough nitrogen removal and stable nitrate nitrogen levels in the effluent. The heterotrophic stage requires only a small amount of organic carbon source for preliminary nitrogen removal, while the autotrophic stage uses reduced sulfur as an electron donor, eliminating the need for additional organic carbon sources and reducing carbon source addition costs. Simultaneously, the slow proliferation of autotrophic microorganisms results in sludge production far lower than that of a single heterotrophic process, reducing sludge treatment and disposal costs.

The application relates to the field of environmental microorganism technology and discloses a salt-tolerant aerobic denitrification bacterium and a method for simultaneously realizing denitrification and carbonate precipitation and carbon fixation. Zobellella denitrificans A36, which is preserved in the Guangdong Microbial Culture Collection Center and has a preservation number of GDMCC No: 66789 and a preservation date of August 7, 2025. The Zobellella denitrificans A36 has complete denitrification key functional genes and carbonic anhydrase related gene clusters; can induce the formation of carbonate precipitation in a salt-containing heterotrophic denitrification system, fixes CO2 generated by the system into inorganic carbonate, and effectively reduces CO2 emission. Under preferred conditions, the removal rate of nitrate nitrogen can reach 93.8%, and stable carbonate carbon fixation effect is realized.

This invention belongs to the field of crop cultivation technology and discloses a method for rapid generation of lettuce. The method involves: hydroponically cultivating lettuce seeds into seedlings, which are then transplanted after reaching the stage of two leaves and one bud; the seedlings are then cultured in a hydroponic tank with a total nitrogen nutrient solution at a nitrogen concentration of 9.0 mmol / L, a temperature of 25℃, and a light intensity maintained at 200 μmol·m² for the first 5 days. ‑2 ·s ‑1 The photoperiod is 16:8, the light quality is red:blue:far-red = 6:1:1, and the light intensity is increased to 320 μmol·m⁻¹ starting from day 6. ‑2 ·s ‑1 The photoperiod was 16:8, the light quality was red:blue:far-red = 6:1:1, and the plants were cultured for 15 days. The cultured lettuce plants were then placed in a low-nitrogen nutrient solution with a nitrogen concentration of 1.5 mmol / L at 25℃ and a light intensity of 320 μmol·m⁻¹. ‑2 ·s ‑1 The photoperiod was 20:4, and the light quality was red:blue:far-red = 6:1:1. The plants were cultured until flowering. After flowering, the nitrogen concentration of the low-nitrogen nutrient solution was adjusted to the normal nitrogen concentration of 9.0 mmol / L until the seeds matured. This invention promotes rapid flowering and seed setting in lettuce, shortens the breeding cycle, and accelerates the lettuce breeding process.

This invention relates to a method for on-site detection of nitrate nitrogen, belonging to the field of water quality testing and monitoring technology. The detection method includes the following steps: collecting a test sample using a water sampler, filtering the sample, mixing the filtered sample with an indicator, and then performing a colorimetric reaction; during the colorimetric reaction, adding concentrated sulfuric acid, deionized water, and a 30-35% sodium hydroxide solution sequentially with the test sample; after the above steps are completed, measuring the absorbance value, and calculating the nitrate nitrogen concentration in the test sample using a standard linear equation. The water sampler and detection method of this invention have high precision and accuracy, and can be used for rapid on-site quantitative detection of nitrate nitrogen concentration in water.

The application discloses a nitrogen-potassium synergistic fertilization method suitable for alfalfa planting in saline-alkali soil and belongs to the technical field of agricultural fertilization. In view of the fact that alfalfa fertilization methods for saline-alkali soil are lacked in the prior art, the nodule bacteria nitrogen fixation cannot be excited by nutrient synergy, nitrogen fertilizer is highly dependent, and the utilization rate is low, the application scheme comprises the following steps: determining the rhizosphere soil conductivity before sowing or before the green stage to divide the saline-alkali stress degree, and determining the nitrate nitrogen content; according to the mass ratio of nitrogen to potassium oxide in the fertilizer is dynamically adjusted according to the nitrate nitrogen content and the saline-alkali degree, when the soil nitrate nitrogen is low, the standard ratio is selected according to the saline-alkali degree, when it is moderate, the nitrogen is halved, and when it is sufficient, the nitrogen fertilizer is stopped; the exogenous nitrogen fertilizer is applied twice from the green stage to the initial flowering stage, the potassium fertilizer containing potassium fulvate is once deep applied from the green stage to the branching stage, and the potassium supply amount of the potassium fulvate is not less than 30% of the total potassium amount. The method is mainly used for alfalfa planting in saline-alkali soil, realizes nitrogen-potassium synergistic high-efficiency utilization, and relieves the saline-alkali stress.

The utility model belongs to underground water processing technical field, concretely relates to integrated treatment device of underground water. Including the filter that washes itself, bag type filter, ion exchanger, sedimentation tank, sand filter tank and disinfection tank that connect in proper order, ion exchanger's export is equipped with water quality detector, still including the regeneration system that links to each other with ion exchanger, and the regeneration system includes the brine tank, brine pump and brine filter that connect in proper order, and brine filter's export links to each other with ion exchanger's regeneration liquid import, ion exchanger and the cleaning fluid export of filter that washes itself links to each other with denitrification filter bed respectively, and the export of denitrification filter bed is connected to brine tank recycling through pipeline, still including PLC control system. Through PLC control system coordination each processing unit, realize the efficient removal of underground water suspended solids and nitrate nitrogen, utilize regeneration system to promote resin utilization rate simultaneously, through denitrification filter bed recycling cleaning fluid, reach the purpose that the treatment effect is stable, the resource is saved.

This application relates to a method and its application for reducing nitrate nitrogen to ammonia nitrogen in wastewater using a dual-bacterial inoculant. The method involves separately expanding, washing, and resuspending electron-donating bacteria and dissimilatory nitrate-reducing ammonium-producing bacteria, then mixing them in a co-culture medium to form a dual-bacterial inoculant; introducing the co-culture medium containing the dual-bacterial inoculant into the wastewater to be treated, and reducing nitrate nitrogen to ammonia nitrogen in the wastewater under anaerobic conditions. This method can reduce nitrate nitrogen in wastewater into a high-energy-density energy storage substance, and can also alleviate the problems of low utilization rate of ammonium nitrogen fertilizer and non-point source pollution, which is of great value for nitrogen pollution control and green sustainable agricultural development.

This invention relates to the field of wastewater treatment technology, and more particularly to an electrocatalytic electrode for ammonia nitrogen wastewater, comprising an ammonia nitrogen catalytic oxidation anode and a nitrate nitrogen reduction cathode. The ammonia nitrogen catalytic oxidation anode comprises a Ti2 substrate; the Ti2 substrate is a hollow cylindrical structure with an open top and closed bottom, and its outer surface is coated with a catalytic oxidation coating, while its inner surface is coated with an anode ClO·capture coating. The nitrate nitrogen reduction cathode comprises a porous biomass nano-carbon felt; the porous biomass nano-carbon felt is a hollow cylindrical structure with an open top and closed bottom, and its outer surface is coated with a cathode reduction coating, while its inner surface is coated with a cathode ClO·capture coating. This invention also discloses its preparation method, an electrode system including the electrode, and a method for using the electrode system. This invention can reduce the selectivity of nitrate nitrogen at the source, achieving complete removal of nitrogen from wastewater.

The present application belongs to the technical field of sewage treatment, and particularly relates to a treatment system and method for sludge bulking caused by filamentous bacteria. The method comprises: performing starvation operation on a sewage biological treatment system in which filamentous bacteria bulking occurs, wherein the starvation operation is to stop or reduce the supply of organic carbon, nitrogen and phosphorus to the sewage biological treatment system; and after the starvation operation, performing supplemental nitrate water feeding on the sewage biological treatment system, wherein the supplemental nitrate water feeding comprises: resuming the supply of water containing an organic carbon source to the sewage biological treatment system, while increasing the concentration of nitrate nitrogen in the water. Through two-stage regulation of “starvation operation + nitrate supplement”, the present application precisely utilizes the metabolic disadvantage of filamentous bacteria under low substrate conditions and the sensitivity of filamentous bacteria to a nitrate environment, so as to selectively inhibit the growth of filamentous bacteria and quickly restore the settling performance of the reactor in a short period of time.

This invention provides a method and apparatus for deep nitrogen removal from low C / N ratio wastewater using a coupled sulfur-iron autotrophic denitrification process, belonging to the field of advanced wastewater treatment technology. The method includes inoculating sludge into a hydrolysis-acidification reactor and a sulfur-iron autotrophic denitrification reactor, respectively; adding biofilm packing and hydrolytic enzyme packing to the hydrolysis-acidification reactor; adding sulfur-iron packing to the sulfur-iron autotrophic denitrification reactor; pumping effluent into the hydrolysis-acidification reactor for preliminary denitrification to form a pretreated product; and sending the pretreated product from the hydrolysis-acidification process into the sulfur-iron autotrophic denitrification reactor for deep autotrophic denitrification. This coupling of the hydrolysis-acidification reactor and the sulfur-iron autotrophic denitrification reactor allows denitrifying bacteria to remove most of the nitrate nitrogen from the hydrolyzed organic matter. The sulfur-iron autotrophic denitrification process, because it does not require an external organic carbon source, has advantages such as reduced organic matter residue, less sludge production, lower sludge treatment costs, good denitrification effect, and less secondary pollution.

The application discloses a kind of sewage treatment plant residual sludge denitrification digestion methods, belong to sludge treatment technical field.The method is introduced into the sludge pool of sewage treatment plant with nitrate nitrogen material, and mix with residual sludge in pool;Denitrifying bacteria group in sludge is with organic matter carried by sludge itself as carbon source, nitrate nitrogen is reduced to nitrogen;Organic matter in sludge is oxidized and decomposed in the reaction process, realize the inorganic of sludge, stabilization and reduction.The application does not need to purchase carbon source and commercial bacterial agent, utilize existing sludge pool, low investment, low operating cost.Nitrate nitrogen material can be derived from in-plant nitrification liquid, external nitrate-containing waste liquid, NO2 generated by catalytic oxidation of ammonia-containing waste material etc..Sludge pool can be used as resource utilization workshop, and a variety of waste is treated in coordination, and the application method of concentrated residual sludge in denitrification treatment submitted on the same day forms technical complementation.

To address the problem of high false alarm rates and severe missed detections in urban wastewater treatment processes due to random interference, sensor malfunctions, and dynamic fluctuations in multivariate time-series data, which significantly impacts the reliability of monitoring data, this invention proposes an adaptive anomaly detection method for urban wastewater treatment processes based on global stability scoring. First, multivariate time-series data, including influent pH and nitrate nitrogen concentration in the anoxic tank, are collected and a data matrix is ​​constructed. Second, a global stability scoring mechanism integrating coefficient of variation, skewness, kurtosis, and entropy is established to quantify the global distribution characteristics and stable state of the data. Then, based on the stability score, the statistical threshold multiple and window size are adaptively determined, and the sliding window parameters are optimized by combining local fluctuation responses. Finally, an adaptive anomaly detection strategy is designed to accurately detect outliers in the multivariate time-series data, ensuring the reliability of monitoring data and guaranteeing the efficient and stable operation of the urban wastewater treatment process.

This invention provides a method for treating farmland drainage using an aerated ecological filter, relating to the field of wastewater treatment technology. The aerated ecological filter comprises, from top to bottom, a coarse-particle packing layer, an aeration device, a filter screen, a Fe-BC@CS-MOF porous material layer, another filter screen, and a fine-particle packing layer. Pseudomonas taiwanensis and Pseudomonas chengduensis are introduced into the aerated ecological filter for cultivation and acclimatization, which converts nitrate nitrogen in farmland drainage into ammonia nitrogen and degrades organic pollutants, reducing COD in the water. The Fe-BC@CS-MOF porous material layer can adsorb ammonia nitrogen, phosphate, and heavy metals. Ammonia nitrogen and phosphate are desorbed through acid leaching, while heavy metals are retained in the porous material, allowing for the recovery and reuse of ammonia nitrogen and phosphate.

This invention provides a *Pseudomonas plecoglossicida* strain, its inoculant, and its applications, relating to the field of microbiology. Specifically, the *Pseudomonas plecoglossicida* NT strain, with accession number CGMCC No. 25090, can efficiently convert nitrate nitrogen, reduce the accumulation of nitrates in soil, and remediate secondary salinized soils. It also possesses the ability to produce extracellular polysaccharides, promoting the formation of soil aggregates and increasing soil cohesion. Furthermore, this strain can successfully colonize the rhizosphere soil of vegetables, improving the rhizosphere ecological environment, promoting vegetable growth, and increasing yield. This achieves the goal of ensuring both the sustainable development of modern agriculture and the quality and quantity of crops. The strain of this invention has relatively comprehensive soil remediation capabilities and has enormous application potential.

This invention relates to the field of wastewater denitrification technology, and particularly to a method based on S n 2‑ A method and system for one-stage PD / A deep denitrification using a mediated effect includes: constructing a biofilm reaction system by setting up a biofilm carrier component and inoculating it with activated sludge in a continuous flow reactor; simulating the preparation of wastewater effluent containing nitrate nitrogen and introducing a polysulfide solution as an electron donor, then independently and continuously adding both to the continuous flow reactor and mixing them uniformly by stirring; adding ammonia nitrogen to the wastewater effluent and inducing in-situ enrichment of anaerobic ammonia oxidizing bacteria in the biofilm reaction system by staged control of the ammonia nitrogen load in the wastewater effluent; and achieving stable coupling of short-cut denitrification and anaerobic ammonia oxidation in a one-stage continuous flow reactor to simultaneously remove nitrate nitrogen and ammonia nitrogen from the wastewater effluent. This invention features a simple start-up method, stable operation, low dependence on external organic carbon sources, and low sludge yield, making it suitable for deep denitrification treatment of urban wastewater with low carbon-to-nitrogen ratios and wastewater treatment plant effluent.