Improved multi-stage ao coupled high ammonia-nitrogen wastewater treatment process and system

Abstract

The application discloses an improved multi-stage AO coupled high-ammonia-nitrogen wastewater treatment system and process. The process core is an AOAO process, which sequentially comprises a first-stage anoxia, a first-stage oxygenation, a second-stage anoxia, a second-stage oxygenation and a sludge-water separation and backflow step. The first-stage oxygenation tank adopts a four-in-one regulation system of DO gradient, FA / pH cooperation, biological membrane enrichment and SRT control, and can stably maintain a short-cut nitrification state. The system comprises core treatment units such as a hydrolysis acidification tank, various-stage anoxia / oxygenation tanks and a secondary sedimentation tank which are connected in series along a water flow, and a layered cooperative control framework composed of a field rapid controller and a central intelligent control unit. The field rapid controller realizes millisecond-level closed-loop control of FA / pH, and the central intelligent control unit overall plans global parameter optimization. The application effectively solves problems such as short-cut nitrification instability and regulation lag in traditional processes, can modularly reform existing systems, reduces investment and operation costs, improves denitrification efficiency, and is suitable for high-ammonia-nitrogen wastewater treatment.

Description

Technical Field

[0001] This invention relates to the field of high ammonia nitrogen wastewater technology, specifically to an improved multi-stage AO coupled high ammonia nitrogen wastewater treatment process and system. Background Technology

[0002] High-efficiency, deep denitrification biological processes are the mainstream technology for treating industrial wastewater with high ammonia nitrogen levels. However, existing processes have the following key drawbacks when treating complex, high-concentration industrial wastewater: 1. High-efficiency, deep denitrification biological processes are the mainstream technology for treating high-ammonia-nitrogen industrial wastewater. However, traditional processes face two fundamental bottlenecks when treating complex, high-concentration industrial wastewater: Carbon source imbalance and inhibition: The high proportion of recalcitrant COD in wastewater leads to a severe shortage of effective carbon sources that can serve as electron donors for denitrification. To meet nitrogen removal requirements, traditional processes have to add large amounts of purchased carbon sources (such as methanol), resulting in high operating costs. At the same time, excessively high organic loads can inhibit autotrophic nitrifying bacteria.

[0003] Resource consumption bottleneck of traditional pathways: The mainstream "complete nitrification-denitrification" denitrification pathway, because it requires the complete oxidation of ammonia nitrogen to nitrate and then reduction to nitrogen gas, is inherently characterized by high energy consumption (aeration oxygen consumption) and material consumption (denitrification carbon source), resulting in poor economic efficiency.

[0004] Furthermore, many existing high-ammonia nitrogen wastewater treatment facilities employing traditional nitrification-denitrification processes face the dual pressures of upgrading (improving nitrogen removal efficiency) and reducing costs (lowering energy and material consumption). However, existing retrofitting solutions often fall into a dilemma: simple parameter optimization yields minimal results; while demolition and reconstruction or large-scale expansion involve huge investments and long downtime periods. Therefore, there is an urgent need for a modular, intelligent deep nitrogen removal technology retrofitting solution that can fully utilize existing structures to achieve a leap in treatment efficiency and operational economy while minimizing civil engineering modifications.

[0005] 2. The potential and inherent limitations of short-cut nitration processes: To overcome the aforementioned bottlenecks, energy-saving and consumption-reducing short-cut nitrification (nitrite) processes have been extensively studied. Because it only oxidizes ammonia nitrogen to nitrite, it has a high theoretical ammonia nitrogen loading rate (NLR), which studies show can reach 0.4 kg NO3--N / (m³) under optimized conditions. 3The above (d) demonstrates significant potential for high efficiency. However, this process faces severe stability challenges in practical engineering. Recent studies generally agree that achieving and maintaining stable inhibition of nitrite-oxidizing bacteria (NOB) is the core challenge in the engineering of short-cut nitrification. This requires not only precise control of parameters such as free ammonia (FA), dissolved oxygen (DO), and pH, but more importantly, dynamic synergy among these factors. For example, a single dissolved oxygen regulation strategy has been proven insufficient to stably restore system performance; it must be combined with alkalinity, hydraulic retention time, and other factors. Simultaneously, the nitrite accumulation rate of the system is extremely sensitive to fluctuations in influent nitrogen load. Any imbalance in regulation can lead to rapid NOB proliferation, causing the short-cut nitrification process to collapse and become difficult to recover.

[0006] 3. Identify the core technological challenges Therefore, the long-standing unresolved technical challenges in this field can be summarized as: how to construct a reliable method and system that can realize and maintain the dynamic synergy of multiple key parameters such as FA, DO, and pH in the long term, so that the short-cut nitrification process can stably exert its theoretical advantages of high load and low consumption, and thus be applied to the engineering treatment of high-concentration ammonia nitrogen wastewater. Summary of the Invention

[0007] The purpose of this invention is to provide an improved multi-stage AO coupled high ammonia nitrogen wastewater treatment process and system to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: an improved multi-stage AO coupled high ammonia nitrogen wastewater treatment process, comprising the following steps: S1, Primary Anoxic Treatment: Wastewater is introduced into the primary anoxic tank, and mixed liquor from the primary aerobic tank is introduced at the same time, with the reflux ratio controlled; under low oxygen conditions, the carbon source in the wastewater is used to complete the denitrification reaction, and the carbon-nitrogen ratio in the tank is monitored and adjusted online in real time. S2. Primary Aerobic Treatment: Wastewater treated in the primary anoxic stage is sent to the primary aerobic tank. A four-in-one synergistic control system is used to control the nitrification reaction at the short-cut nitrification stage. The four-in-one synergistic control system includes: DO gradient control along the water flow direction, FA / pH synergistic control, biofilm enrichment, and system sludge retention time control. Gradient DO control creates a competitive environment for ammonia-oxidizing bacteria (AOB); FA / pH linkage control selectively inhibits the activity of nitrite-oxidizing bacteria (NOB); biofilm enrichment provides attachment sites and shock protection for ammonia-oxidizing bacteria (AOB); and system sludge retention time (SRT) control selectively washes away NOB and consolidates the dominance of the AOB community. S3, Secondary anoxic treatment: The wastewater treated in the primary aerobic tank is introduced into the secondary anoxic tank. Under anoxic conditions, carbon sources are used to further remove nitrate nitrogen and nitrite nitrogen from the wastewater. The amount of external carbon source added is monitored and adjusted online. S4. Secondary aerobic treatment: The wastewater after secondary anoxic treatment is sent to the secondary aerobic tank, and the DO concentration in the tank is controlled to reach the preset aerobic standard to further oxidize and remove residual pollutants in the wastewater. S5. Sludge-water separation and return treatment: The wastewater after secondary aerobic treatment is sent to the secondary sedimentation tank for solid-liquid separation. The supernatant after separation can be directly discharged in compliance with standards or enter the advanced treatment stage. Part of the sludge generated by sedimentation is returned to the primary anoxic tank to maintain the activity of microorganisms in the system, and the remaining sludge is discharged from the system.

[0009] Preferably, before step S1, a hydrolysis acidification pretreatment step is included: after adjusting the pH value of the wastewater, hydrolysis acidification treatment is performed to hydrolyze and acidify some of the recalcitrant organic matter in the wastewater into volatile fatty acids (VFA).

[0010] Preferably, step S2 is executed and regulated by a hierarchical collaborative control architecture: a field fast controller with a built-in edge computing module is deployed at the primary aerobic tank to achieve millisecond-level ultra-fast closed-loop control of free ammonia and pH; the central intelligent control unit is responsible for global parameter optimization and scheduling, and works with the field fast controller to form a fast-slow decoupled control closed loop.

[0011] Preferably, the specific implementation method of DO gradient control in step S2 is as follows: the primary aerobic tank is divided into multiple series aeration zones along the water flow direction, and the DO concentration in each zone is independently controlled to form a gradient distribution that gradually changes along the water flow direction, adapting to the reaction requirements of different stages of short-cut nitrification; the multiple series aeration zones are preferably divided into four or three zones; when divided into four zones, the DO concentration control range of each zone is: zone 1 0.9-1.2 mg / L, zone 2 0.7-0.9 mg / L, zone 3 0.6-0.8 mg / L, zone 4 0.5-0.7 mg / L; when divided into three zones, the DO concentration control range of each zone is: zone 1 0.9-1.1 mg / L, zone 2 0.6-0.8 mg / L, zone 3 0.5-0.7 mg / L.

[0012] Preferably, in step S2, the FA / pH synergistic regulation utilizes the difference in tolerance of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) to free ammonia (FA). By adjusting the free ammonia concentration and pH value, FA is controlled within a concentration range that selectively inhibits NOB without inhibiting AOB, thereby selectively inhibiting NOB activity and promoting AOB growth and accumulation. The free ammonia (FA) concentration is determined in real time based on parameters including ammonia nitrogen concentration, pH value, and water temperature, and dynamically stabilized within the range of 5–15 mg / L. At low temperatures, it tends to be controlled at the lower limit of the range, and at high temperatures, it is strictly controlled at the upper limit of the range. To stabilize the free ammonia (FA) concentration, three-level regulation is implemented when free ammonia deviates from the target range: normal regulation corrects the free ammonia concentration by adjusting the alkalinity dosage; when free ammonia continues to exceed the standard, the alkalinity dosage is first reduced to lower the pH through nitrification acid production; if the pH still does not meet the standard after dropping to the safe lower limit, the internal reflux ratio is temporarily increased for hydraulic dilution; when the influent ammonia nitrogen seriously exceeds the standard, wastewater storage or segmented influent is initiated; FA / pH The coordinated control adopts a field rapid controller and a central intelligent control unit to jointly execute FA / pH control; the central intelligent control unit calculates the dynamic FA target value online based on parameters including influent ammonia nitrogen, water temperature and alkalinity consumption cost and sends it to the field rapid controller; the field rapid controller performs closed-loop control of FA and pH based on real-time monitored pH, temperature and ammonia nitrogen data.

[0013] Preferably, the biofilm enrichment in step S2 is achieved by setting a biofilm carrier in the primary aerobic tank to provide space for ammonia-oxidizing bacteria (AOB) to attach and grow.

[0014] Preferably, the sludge retention time control in step S2 is to control the system SRT within a range suitable for enriching ammonia-oxidizing bacteria (AOB) and eluting nitrite-oxidizing bacteria (NOB); by intelligently adjusting the amount of excess sludge discharged, and dynamically calculating and optimizing the SRT based on the online monitoring of MLSS concentration, excess sludge concentration and sludge discharge flow rate, precise SRT control is achieved.

[0015] Preferably, in the first-stage aerobic treatment process of step S2, the ammonia nitrogen loading rate (NLR) is used as the core control parameter and controlled within the preset optimization range to ensure efficient AOB metabolism, provide a stable environment for DO gradient regulation and FA / pH synergistic control, and ensure that the nitrite accumulation rate is maintained at or above the preset high value.

[0016] This invention also provides an improved multi-stage AO-coupled high ammonia nitrogen wastewater treatment system. The system is used to implement the above-mentioned treatment process and includes a core treatment unit connected in series along the water flow direction and a hierarchical collaborative control architecture. The core treatment unit includes at least a primary anoxic tank, a primary aerobic tank, a secondary anoxic tank, a secondary aerobic tank, and a secondary sedimentation tank. The hierarchical collaborative control architecture includes a field control unit and a central intelligent control unit. The field control unit is deployed next to the primary aerobic tank and is connected to the monitoring and execution equipment of the primary aerobic tank. The central intelligent control unit is connected to the field control unit and the monitoring and execution equipment of the entire system to realize global parameter optimization and scheduling.

[0017] Preferably, the core treatment unit further includes a hydrolysis acidification tank connected in series upstream of the primary anoxic tank, the hydrolysis acidification tank being equipped with relevant equipment for adjusting water quality, maintaining mixing, and monitoring the environment; the secondary sedimentation tank is equipped with sludge return, excess sludge discharge, and related equipment and monitoring instruments, all controlled by a central intelligent control unit to maintain stable sludge concentration in the system; the primary aerobic tank has multi-level gradient aeration zones and supporting monitoring and control equipment to form a dissolved oxygen gradient distribution adapted to short-cut nitrification requirements; and the primary aerobic tank is equipped with an optional rapid start-up auxiliary device for adding selective inhibitors during system start-up or recovery to accelerate the enrichment of ammonia-oxidizing bacteria; the on-site control unit and The precise monitoring cluster and control actuator of the primary aerobic tank are connected to achieve coordinated control of free ammonia and pH, as well as emergency response. The precise monitoring cluster includes key parameter monitoring equipment for calculating free ammonia concentration, and the control actuator includes related equipment for pH adjustment, hydraulic dilution, and aeration control. The central intelligent control unit has multiple built-in functional control modules, which correspond to the various coordinated control requirements of short-cut nitrification in the primary aerobic tank, carbon source addition, reflux ratio control, and sludge retention time control. The functional control modules include at least a sludge retention time calculation and control module, a dissolved oxygen gradient control module, a free ammonia and pH coordinated control module, and an ammonia nitrogen loading rate control module.

[0018] Compared with the prior art, the beneficial effects of the present invention are: First, this invention comprehensively regulates and coordinates four key parameters—DO gradient regulation, FA / pH synergistic control, biofilm microbial community enrichment, and SRT—to build a multi-dimensional synergistic stability system within the range of 0.12~0.40 kgN / (m 3 ·d) Under high load conditions, the nitrite accumulation rate (NAR) was kept stable at over 85% for a long period of time, successfully solving the core problem of the difficulty in simultaneously achieving NOB inhibition and AOB enrichment, and solving the problem of short-range nitrification instability.

[0019] Second, the present invention adopts a hierarchical intelligent control architecture that coordinates on-site and central control. The on-site control layer is deployed in core units such as the O1 tank to achieve millisecond-level ultra-fast closed-loop control of parameters such as pH and FA. The central optimization layer coordinates the intelligent optimization and scheduling of global parameters such as carbon source addition and sludge discharge, which completely solves the response lag defect of traditional centralized control and overcomes the problem of regulation response lag.

[0020] Third, this invention abandons the traditional fixed parameter control mode and incorporates a control logic that uses the selective inhibition concentration of FA (5~15mg / L) as a constraint and the optimal operating cost as the objective. Based on the real-time influent ammonia nitrogen load and water temperature, it dynamically issues the optimal FA target value and the synergistic pH setting value (7.0~8.5), driving the system to operate at the best balance point between biological stability and operational economy, thereby achieving optimal system operation.

[0021] Fourth, the core process units (DO gradient control in the O1 tank and FA / pH synergistic control subsystem) and intelligent control architecture of this invention adopt a modular design. Each component is independently detachable, allowing for flexible integration and modification with existing A / O and multi-stage A / O process aeration tanks. Modification requires only partial upgrades, eliminating the need for large-scale tank expansion. Downtime for commissioning is short, reducing investment by 40% to 60% compared to traditional reconstruction, achieving the goal of low-investment, quick-results energy-saving and consumption-reducing modifications. It possesses the advantage of flexible modular modification. Attached Figure Description

[0022] Figure 1 This invention provides a process flow diagram and control system diagram for treating high ammonia nitrogen wastewater using a modified multi-stage AO coupling process. Figure 2 This is a schematic diagram of the linkage control between FA and pH provided by the present invention; Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the present invention clear and complete, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only some, not all, embodiments of the present invention, and are merely illustrative of the embodiments of the present invention. They are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Reference Figure 1-2 This invention discloses an improved multi-stage AO-coupled high-ammonia nitrogen wastewater treatment system. The system employs an "AOAO" process, with a hydrolysis acidification tank (HR), a primary anoxic tank (A1 tank), a primary aerobic tank (O1 tank), a secondary anoxic tank (A2 tank), a secondary aerobic tank (O2 tank), and a secondary sedimentation tank connected in series along the water flow direction via pipelines. The hydrolysis acidification tank (HR) is equipped with a pH adjustment device, an underwater agitator, and a DO monitor. It maintains a strictly anoxic environment (DO < 0.2 mg / L), converting some of the recalcitrant organic matter in the wastewater into readily biodegradable volatile fatty acids (VFAs), optimizing the carbon source form, and providing sufficient internal carbon source for subsequent denitrification reactions. This reduces the amount of external carbon source required and lowers operating costs. The "AOAO" process of this system is the preferred implementation. Those skilled in the art can flexibly adjust the process configuration according to actual effluent quality requirements: it can be simplified to an AOA process, expanded to an AOAAO process, only adjusting the number and function of the treatment units after the main coordinating units; alternatively, under specific design conditions, the hydrolysis acidification tank and the pre-anoxic tank can be integrated into a composite unit with dual functions. All these adjustments do not affect the main treatment effect.

[0025] The primary anoxic tank (A1 tank) is equipped with a submersible mixer to maintain the sludge in suspension and ensure the mixing conditions required for denitrification. The inlet of the A1 tank is equipped with an online carbon-to-nitrogen ratio (C / N) monitoring unit and a primary external carbon source intelligent dosing device. The online monitoring unit includes at least an online COD analyzer and a TN analyzer, which can monitor and adjust the C / N ratio within the tank in real time to ensure efficient and stable denitrification.

[0026] The primary aerobic tank (O1 tank), as the core unit of short-cut nitrification, directly determines the stability of short-cut nitrification. An aeration system is installed in this tank to achieve DO gradient control, creating a competitive environment for ammonia-oxidizing bacteria (AOB) while reducing aeration energy consumption. A mixed liquor internal recirculation pipeline and a frequency converter-driven mixed liquor recirculation pump are installed between the primary aerobic tank (O1 tank) and the primary anoxic tank (A1 tank), achieving an internal recirculation ratio (R1) of 200%-400%. This meets the nitrogen removal efficiency requirements and enables rapid hydraulic dilution when FA concentration exceeds the standard, improving the system's shock resistance. Biofilm carrier packing materials (such as elastic three-dimensional packing or fixed-bed plate packing) are added to the tank to provide attachment and growth sites for AOB, strengthening the AOB community advantage and consolidating the short-cut nitrification effect. A rapid start-up auxiliary dosing device, such as a hydroxylamine dosing system, can be installed at the tank inlet to accelerate AOB enrichment during system start-up or recovery, shortening the start-up cycle.

[0027] The secondary anoxic tank (A2 tank) is equipped with a submersible mixer to maintain the sludge in suspension and ensure the mixing conditions required for denitrification. The A2 tank inlet is equipped with an online carbon-to-nitrogen ratio (C / N) monitoring unit and a secondary external carbon source intelligent dosing device. The online monitoring unit can monitor and adjust the C / N ratio within the tank in real time to ensure the denitrification reaction proceeds efficiently and stably.

[0028] The secondary aerobic tank (O2 tank) is equipped with an aeration system (such as a microporous aerator). Its core function is to control the DO concentration in the tank at 2.0~2.5mg / L, ensure uniform mixing, further oxidize and remove residual pollutants in the wastewater, and ensure that the effluent water quality fully meets the standards.

[0029] The secondary sedimentation tank is equipped with a sludge scraper, and the bottom is equipped with a sludge return pipe and a sludge return pump. The sludge return pipe is connected to the primary anoxic tank (A1 tank) to achieve a sludge return ratio of 50%-100% (R2) and maintain the activity of microorganisms in the system. At the same time, the secondary sedimentation tank sludge discharge pipeline is equipped with a residual sludge discharge pump and a flow meter to regulate the amount of residual sludge discharged.

[0030] To achieve intelligent control of the entire system, this system is equipped with comprehensive online monitoring equipment, specifically including: an online mixed liquor suspended solids (MLSS) monitor installed in the primary aerobic tank (O1 tank) to provide data support for SRT control; and an online sludge concentration meter installed on the sludge return pipeline to monitor the return sludge concentration (X) in real time. RAS ); A residual sludge concentration (X) meter can be added to the residual sludge discharge pipeline. WAS The online monitoring instrument further improves the accuracy of SRT control and provides precise data support for intelligent control.

[0031] In the control actuators of this system, the residual sludge discharge pump is a variable frequency pump or controlled by an electric regulating valve. It can automatically adjust the residual sludge discharge flow rate according to the instructions of the central intelligent control unit, so as to achieve precise control of SRT and reduce manual intervention.

[0032] The primary aerobic tank (O1 tank) serves as the core unit of short-cut nitrification and is equipped with two core control subsystems. The two work together to form a "multi-dimensional collaborative stabilization system" for short-cut nitrification, ensuring long-term stability of short-cut nitrification. The multi-level gradient DO control subsystem is the key to achieving short-cut nitrification. Its core is to form a gradually decreasing DO gradient along the water flow direction in the O1 tank through zoned aeration and precise control. In practice, the O1 tank is divided into multiple aeration zones (preferably three or four) along the water flow direction. A high-precision DO sensor (accuracy ±0.05mg / L) is installed at the end of each zone to monitor the DO concentration in real time. Each zone is equipped with an independent variable frequency aeration device (such as a microporous aerator), and the aeration intensity is controlled by a variable frequency drive (VFD). The blower speed or valve opening is dynamically adjusted according to the deviation between the measured DO value and the set value of each zone, so as to achieve a stepwise decrease in DO concentration from the inlet to the outlet along the water flow direction (for example, four zones: 0.9~1.2mg / L→0.7~0.9mg / L→0.6~0.8mg / L→0.5~0.7mg / L). To further expand the applicability and operational flexibility of DO gradient control, equivalent DO distribution effects can be achieved through diverse control methods. These include adjusting the number of zones, optimizing the aeration method, or changing the operating sequence. All of these can create DO distribution patterns conducive to AOB enrichment and NOB suppression. These methods include employing two-, three-, or more levels of zoned control; achieving continuous and smooth DO changes through non-uniform aeration or flow field optimization design; and using intermittent aeration or alternating aerobic / anoxic operation strategies to achieve stable DO control effects over time. A stable DO gradient distribution can sustainably suppress nitrite-oxidizing bacteria (NOB) activity and optimize the metabolic environment for ammonia-oxidizing bacteria (AOB).

[0033] The precise FA and pH synergistic control subsystem, in conjunction with the DO gradient control subsystem, constitutes a dual "chemical-physical" stabilization mechanism for short-cut nitrification, which is the core of ensuring the long-term stability of short-cut nitrification. The monitoring unit of this subsystem is located in the middle section of the O1 tank, including a high-precision pH meter (accuracy ±0.02, with automatic cleaning and temperature compensation functions), a temperature sensor (accuracy ±0.1℃), and an online ammonia nitrogen analyzer sampling port. It can collect key parameters such as pH, temperature, and ammonia nitrogen concentration in real time, providing accurate data for FA concentration calculation. A field rapid controller is independently deployed beside the O1 tank, with a built-in edge computing module. The field rapid controller directly connects to the pH meter, temperature sensor, and online ammonia nitrogen analyzer signals in this tank. Based on the real-time monitored pH, temperature, and ammonia nitrogen concentration, it calculates the free ammonia (FA) concentration according to the dynamic pKa model and compares it with the set target range for FA. The actuator includes a high-precision metering pump, which is used for rapid and precise addition of alkali solution to adjust the pH, and is directly controlled by the field rapid controller.

[0034] The on-site rapid controller (with a built-in edge computing module) is independently deployed beside the O1 tank, enabling the aforementioned precise and coordinated control. Because the FA concentration changes rapidly with the reaction process, and the control window is short, the edge computing module can achieve a millisecond-level monitoring-calculation-execution closed loop. This avoids network latency and control lag caused by uploading calculation tasks to the central PLC, ensuring timely and accurate control and further guaranteeing stable short-range nitration operation. This localized closed-loop control, in conjunction with the central intelligent unit, achieves a response time of ≤2 seconds for key process parameters, completely changing the traditional situation of isolated control and slow response of process parameters.

[0035] The control logic of this subsystem is as follows: the on-site rapid controller adjusts the amount of alkali added quickly based on the real-time deviation of the FA concentration to achieve normal feedback regulation; when the FA concentration continues to exceed the standard, it can request the central intelligent control unit to temporarily increase the internal reflux ratio for emergency hydraulic dilution regulation.

[0036] This system adopts a hierarchical distributed architecture of "field fast controller (edge ​​computing) + central intelligent control unit". The central intelligent control unit serves as the global scheduling core, communicating with the monitoring instruments and actuators of the entire system to achieve intelligent control of the entire process. Its specific functions are as follows: This system adopts a hierarchical distributed architecture of "field fast controller (with built-in edge computing module) + central intelligent control unit" (it can also be implemented through various hardware forms such as a single centralized PLC, DCS, or cloud-based Internet of Things (IoT) system, as long as the same control functions can be achieved). This architecture can significantly improve the reliability and consistency of system operation. This intelligent architecture realizes the transformation from traditional "manual intervention and isolated control" to "intelligent collaboration and real-time adjustment", greatly improving the reliability and consistency of system operation.

[0037] Data aggregation and monitoring functions: Real-time reception of operational data from all monitoring points in the entire system, including DO concentration, pH value, FA concentration, MLSS concentration, reflux ratio, carbon source dosage, sludge discharge, etc., enabling centralized display, storage and trend analysis of data, providing data support for process optimization.

[0038] Intelligent adjustment module for FA / PH parameters: With a built-in process optimization model, the module can calculate and send the optimal process setting target (such as dynamic FA target value and pH setting range) to the FA / pH field rapid controller online based on the real-time monitored influent water quality (ammonia nitrogen, C / N), water volume, water temperature and preset cost weights, ensuring that the FA / PH parameters always operate at the best balance point between biological stability and operational economy.

[0039] Carbon source dynamic dosing module: Based on the online C / N monitoring data at the A1 tank inlet, it automatically controls the primary external carbon source dosing rate; simultaneously, based on the online TN analyzer reading at the A2 tank inlet, it calculates the dosing rate according to the formula Q=k×C. TN Dynamically control the amount of secondary external carbon source added to achieve precise carbon source delivery and avoid waste.

[0040] Internal reflux ratio intelligent control function: ensures that the mixed liquor reflux pump operates at the rated design reflux ratio (R1_design) that meets the denitrification efficiency. When an emergency request is received from the O1 pool field fast controller due to FA exceeding the limit, the mixed liquor reflux pump is instructed to temporarily increase the reflux ratio based on R1_design for dilution. After FA recovers, it is instructed to return to the baseline operation.

[0041] SRT Intelligent Calculation and Control Function: Built-in SRT calculation and control module, based on online monitoring of mixed liquor sludge concentration (X) and excess sludge concentration (X). WAS ) and emission flow (Q w According to the formula Calculate the current sludge age in real time.

[0042] By dynamically adjusting the frequency of the residual sludge discharge pump or the valve opening through a closed-loop control algorithm, the SRT can be stabilized within the target range of 10 to 15 days.

[0043] Collaboration with the field layer: Sends the set thresholds of the short-cut nitrification core process (such as the target range of FA and the stable pH range) to the field rapid controller of the O1 tank; receives and stores high-frequency data such as FA concentration, temperature, and pH uploaded by the field rapid controller in real time; receives emergency requests from the field rapid controller and immediately issues global collaborative instructions such as increasing the internal reflux ratio.

[0044] It should be noted that the layered distributed architecture of this system can be implemented in various hardware forms and is not limited to specific equipment models. As long as it can achieve the collaborative function of millisecond-level closed-loop control on site and central global optimization, it can greatly improve the reliability and consistency of system operation.

[0045] Based on the aforementioned system architecture, this invention offers significant advantages in the retrofitting of existing systems. Compared to traditional demolition and reconstruction methods, its application value is more prominent, specifically in the following aspects: In terms of investment costs, the retrofit primarily focuses on upgrading the core control module and local aeration systems, eliminating the need for large-scale expansion of the tank capacity and significantly reducing civil engineering investment. Regarding the retrofitting period, the modular design supports phased implementation, minimizing system downtime or reduced production time, shortening the retrofitting cycle by more than 50% compared to traditional reconstruction methods. In terms of cost-effectiveness, after the retrofit, the system can achieve a 25-35% reduction in energy consumption and a 40-60% reduction in external carbon source dosage while maintaining or increasing the treated water volume. Furthermore, in terms of operation and management, the original operation mode reliant on manual experience can be upgraded to full-process intelligent collaborative control, significantly reducing the difficulty of operation and management and the risk of human error, thereby improving the operational efficiency after the retrofit. Building upon this foundation, the present invention further enhances the level of intelligent operation and optimizes the manual intervention mode. Specifically, in terms of intelligent operation and optimized manual intervention, the present invention abandons the traditional process that requires real-time monitoring and manual adjustment of parameters such as pH, DO, and FA, which is highly dependent on operational experience and prone to process instability due to human error. The present invention constructs a hierarchical control architecture that coordinates on-site and central operations. The core control loop of the O1 tank (FA-pH-internal reflux coordination) is independently completed by the on-site rapid controller, avoiding the delay caused by remote signal transmission and central processor scanning in the traditional architecture. This makes the adjustment actions more timely. The entire process, including carbon source addition and sludge discharge, is coordinated and optimized by the central intelligent unit. Overall, the key process parameters are automatically optimized and stably controlled, reducing the frequency of daily manual intervention by approximately 80% and significantly improving operational reliability and consistency.

[0046] Based on the above system design, this invention provides an improved multi-stage AO coupled high ammonia nitrogen wastewater treatment process, the detailed implementation steps of which are as follows: Firstly, a hydrolysis-acidification pretreatment step can be added based on the actual wastewater quality requirements. For high-ammonia nitrogen wastewater, the pH value is first adjusted to a suitable range before being sent to the hydrolysis-acidification tank. The DO concentration in the tank is controlled below 0.2 mg / L, and the hydraulic retention time (HRT) is controlled between 12 and 16 hours. Under the action of an underwater agitator, the sludge and water are thoroughly mixed, causing some of the recalcitrant organic matter in the wastewater to hydrolyze and acidify into volatile fatty acids (VFAs), optimizing the carbon source form and improving the wastewater's biodegradability (B / C ratio), providing sufficient internal carbon source for subsequent denitrification. This pretreatment step can be replaced with anoxic / anaerobic biological units such as anaerobic or facultative anaerobic tanks, or coupled with advanced oxidation technologies such as Fenton's reagent and ozone, depending on actual needs. All of these methods can achieve the carbon source optimization goal without affecting the main process effect. If no pretreatment is required, the raw water can be directly sent to the primary anoxic tank for treatment.

[0047] The wastewater, after pretreatment by hydrolysis and acidification (or raw water if no pretreatment is used), enters the S1 and primary anoxic tank (A1). Simultaneously, the mixed liquor produced in the primary aerobic tank (O1) is introduced into the A1 tank through an internal return pipe, controlling the internal return ratio (R1) at 200%-400%. During operation, a submersible mixer maintains the sludge in suspension, controlling the DO concentration in the tank to not exceed 0.5 mg / L, and the denitrification rate to be maintained at 0.04~0.08 kg NO3. - -N (kgMLSS / d); Sufficient denitrification of nitrate / nitrite nitrogen in the return liquid is achieved using internal and supplementary carbon sources. The influent COD and TN concentrations are monitored in real-time by the online COD and TN analyzers of the C / N online monitoring unit at the A1 tank inlet. The carbon-to-nitrogen ratio is calculated. When the real-time C / N ratio falls below the set threshold of 3:1, the intelligent control system automatically initiates the primary external carbon source addition program, adding carbon sources such as methanol or sodium acetate to ensure that the C / N ratio in the A1 tank remains within the efficient denitrification range, preventing incomplete nitrogen removal due to insufficient carbon sources.

[0048] After treatment in the primary anoxic tank (A1), the wastewater enters the S2 and primary aerobic tank (O1) treatment stages. The wastewater treated in tank A1 is then sent to the primary aerobic tank (O1), which is essentially a short-cut nitrification reactor. This step is crucial to the invention, its core being the long-term stable inhibition of nitrite-oxidizing bacteria (NOB) through a multi-dimensional synergistic inhibition strategy: ① creating a fluid environment that provides a competitive advantage for ammonia-oxidizing bacteria (AOB) through dissolved oxygen gradient control; ② selectively inhibiting NOB through FA / pH linkage control or direct application of selective chemical inhibition; ③ optimizing the microbial niche through biofilm enrichment and SRT control. These three elements are interconnected and synergistic, collectively forming the technical system for maintaining the stable operation of the short-cut nitrification system. To accelerate the establishment of short-cut nitrification, rapid start-up support measures can be taken during the system start-up or recovery period. Specifically, hydroxylamine (NH2OH) can be added to the O1 tank as a selective inhibitor. The initial concentration can be 3-5 mg / L, and the concentration can be dynamically adjusted according to the accumulation of nitrite in the system. The addition can be continued for 3-7 days to rapidly inhibit the activity of nitrite-oxidizing bacteria (NOB), promote the enrichment of ammonia-oxidizing bacteria (AOB), and accelerate the establishment of short-cut nitrification.

[0049] Multi-level gradient DO regulation, as a core component of a multi-dimensional synergistic inhibition strategy, aims to achieve sustained inhibition of nitrite-oxidizing bacteria (NOB) and optimize the metabolic environment of ammonia-oxidizing bacteria (AOB). Within the O1 tank, which serves as the core of short-cut nitrification, multiple aeration zones are connected in series along the water flow direction. This results in a gradient decrease in dissolved oxygen (DO) concentration in each zone along the flow path, with the overall DO gradient controlled between 1.2 mg / L and 0.5 mg / L. This design is based on the typical difference in dissolved oxygen affinity between AOB and NOB: AOB maintains metabolic activity even in low DO environments (typically not lower than 0.5 mg / L), while NOB activity is significantly inhibited when DO remains below 1.0 mg / L.

[0050] To achieve the aforementioned DO gradient distribution, the O1 tank reactor can be divided into multiple functional zones, preferably three or four zones for independent and coordinated control. In a four-zone configuration, the first zone (inlet end) along the water flow direction controls DO at 0.9–1.2 mg / L to ensure the initial reaction rate under high ammonia nitrogen load and rapid AOB startup. The second and third zones control DO at 0.7–0.9 mg / L and 0.6–0.8 mg / L respectively, gradually reducing DO concentration to continuously enhance selective inhibition of NOB while maintaining effective AOB metabolism, collectively forming the core nitrification reaction zone. The fourth zone (outlet end) controls DO at 0.5–0.7 mg / L to maintain the lowest possible DO level for ultimate inhibition of residual NOB and ensure complete ammonia nitrogen conversion. This stabilizes the nitrite accumulation rate in the system. If a three-zone configuration is adopted, its control logic and functional division are consistent with the four-zone scheme, corresponding to Zone 1 (0.9~1.1mg / L), Zone 2 (0.6~0.8mg / L), and Zone 3 (0.5~0.7mg / L). Each zone is equipped with an independent high-precision DO sensor (accuracy ±0.05mg / L) and an aeration unit controlled by a variable frequency drive (VFD). The VFD system dynamically adjusts the fan speed or valve opening based on the real-time deviation between the DO set value and the measured value of each zone. This multi-level gradient DO control strategy, as a key measure to ensure the stable operation of the short-cut nitrification-denitrification system, not only creates a stable biochemical reaction space conducive to AOB enrichment, but also achieves significant energy saving in aeration through precise on-demand oxygen supply.

[0051] The design and operation of the O1 tank uses ammonia nitrogen loading rate (NLR) as the core control parameter, which is controlled between 0.2 and 0.4 kg NH4. + -N / (m 3 In the optimization range of ·d), when the average winter temperature is below 16℃, it is recommended to take the lower limit value to provide a stable environment for DO gradient regulation and FA / pH synergistic control, ensuring that the nitrite accumulation rate (NAR) remains stable above 85% in the long term. Simultaneously, adding biofilm carrier packing materials (such as elastic three-dimensional packing materials or fixed-bed flat packing materials) to the O1 tank provides an attachment and growth surface for AOB, enhancing system stability. The stable operation of the above-mentioned short-cut nitrification and the efficient synergy of the entire system rely on the support of a multi-synergistic stability maintenance and regulation technology system. In terms of treatment efficiency and load carrying capacity, this invention effectively overcomes the ammonia nitrogen load limitation of traditional nitrification processes by constructing a multi-synergistic stability maintenance and regulation technology system (i.e., a comprehensive regulation system combining DO gradient regulation, FA / pH synergistic regulation, SRT regulation, and emergency regulation of internal reflux ratio). To ensure operational stability, traditional nitrification processes typically control the ammonia nitrogen load rate (NLR) corresponding to the designed tank volume at 0.06-0.20 kgNH4. + -N / (m 3The conservative range of ·d) is not met, but in actual operation, the present invention can stably increase NLR to 0.12-0.40 kgNH4. + -N / (m 3 ·d). Based on this load-boosting effect, in engineering scenarios with the same treatment scale, the total volume of the bioreactor required by this invention can be reduced by about 30-40%, thereby significantly reducing the land area required, lowering infrastructure investment costs, and improving the economic efficiency of engineering construction; In terms of operating cost control, this invention achieves multiple savings in energy consumption, carbon consumption, and sludge disposal costs through process optimization. Regarding aeration energy consumption, this invention maintains a short-cut nitrification reaction path throughout the process, theoretically saving 25% of aeration oxygen demand compared to the traditional complete nitrification path. Simultaneously, combined with a multi-stage gradient precision aeration control strategy in the primary aerobic tank, it effectively avoids over-aeration, achieving a synergistic effect of theoretical and actual energy savings, resulting in a significant reduction in the overall aeration energy consumption of the system. Regarding external carbon source consumption, the short-cut nitrification-denitrification path itself can theoretically save approximately 40% of carbon source compared to the traditional complete nitrification-denitrification path. Building upon this, this invention further enhances the internal carbon source substitution rate and eliminates carbon source waste through optimized internal carbon source supply via hydrolysis acidification pretreatment and a two-stage intelligent precision dosing strategy. In practical engineering applications, this ultimately achieves a comprehensive carbon-saving effect of reducing the amount of purchased carbon source by 50-70%. In addition, since the microbial yield coefficient in the short-cut nitrification-denitrification pathway is lower than that in the complete nitrification-denitrification pathway, the residual sludge production of the system can be reduced by about 15-25%, effectively reducing the cost of sludge disposal.

[0052] As another core technology of the multidimensional synergistic inhibition strategy, the linkage control of free ammonia (FA) and pH can be used in conjunction with selective chemical inhibition methods to achieve precise and selective inhibition of nitrogen oxides (NOB), ensuring the long-term stable operation of the short-cut nitrification system. The principle of free ammonia (FA) control lies in the significant difference in FA tolerance between ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB): studies have confirmed that NOB is extremely sensitive to FA, and its activity is effectively inhibited when the FA concentration is consistently above 0.1–1.0 mg / L; while AOB's tolerance is much stronger, and its activity is typically significantly inhibited only when the FA concentration is consistently above 10–20 mg / L. Therefore, the key to achieving and maintaining stable short-cut nitrification is to construct and maintain a "selective FA inhibition concentration range" in the biochemical system. This range must be significantly higher than the NOB inhibition threshold to continuously suppress NOB; at the same time, it must be strictly lower than the AOB inhibition threshold to protect the core functional bacterial community. Based on this, the control system of this invention sets the safe operating limit of FA at 15 mg / L, providing sufficient protection margin for the AOB bacterial community.

[0053] The concentration of ammonia (FA) is determined by pH, water temperature, and ammonia nitrogen concentration. The core calculation formula is as follows: 1. Temperature correction formula for the dissociation constant (pKa) of ammonia: ; Where T is the water temperature (°C).

[0054] 2. Formula for calculating free ammonia (FA) concentration: ; in, The concentration is ammonia nitrogen (mg / L).

[0055] Based on the aforementioned calculation model, controlling the parameters affecting FA concentration to maintain it within a suitable range is the core measure for ensuring the stable operation of a short-cut nitrification-denitrification system. The target FA value is not fixed but dynamically calculated by the central intelligent control unit based on real-time influent ammonia nitrogen concentration, water temperature, and an optimization algorithm considering reagent (alkali) consumption costs. The system needs to dynamically stabilize the FA concentration within the aforementioned "selective inhibition concentration range," for example, 5-15 mg / L. This optimal range can be dynamically adjusted according to the season and operating conditions: at low temperatures (e.g., 10℃), it tends towards the lower limit (e.g., around 5 mg / L) to ensure inhibition effectiveness, reducing unnecessary alkalinity consumption; at high temperatures (e.g., 30℃), the upper limit is strictly controlled, and hydraulic dilution emergency measures are prioritized.

[0056] To achieve precise control of FA concentration and ensure short-range nitrification stability, the system adopts a three-level closed-loop collaborative decision-making and execution logic. The first level is normal feedback regulation: when the real-time FA is lower than the dynamic target, the system slightly increases alkalinity within the safe pH range; conversely, it slightly reduces alkali addition, using pH changes to regulate FA. The second level is shock-resistant collaborative regulation: when the influent ammonia nitrogen exceeds the standard, causing FA to continuously exceed the standard, the alkali addition is first reduced, and the pH naturally decreases to reduce FA by utilizing nitrification acid production. If the pH drops to the safe lower limit (e.g., 7.0) but FA still exceeds the standard, the on-site rapid controller requests the central intelligent control unit to temporarily increase the internal recirculation ratio (R1) from the O1 tank to the A1 tank. By strengthening the dilution of the recirculated liquid, the ammonia nitrogen load entering the O1 tank is reduced from the source, and FA is quickly suppressed. The third level is extended emergency protection: when the influent ammonia nitrogen concentration continuously exceeds 50% of the design value or the absolute safety threshold, the central intelligent control unit triggers emergency procedures, such as temporarily storing the wastewater in the emergency equalization tank / starting segmented influent, providing ultimate protection for the core microbial community. To counteract the natural influence of temperature on FA concentration and ensure the stability of FA selective inhibition, the system can automatically adjust the pH setpoint based on the relationship model between pKa and temperature. Specifically, for every 10°C increase in temperature, the pH setpoint needs to be lowered by approximately 0.20 units to achieve dynamic and stable control of FA concentration.

[0057] Based on the dynamic and precise control of FA concentration, combined with the previously mentioned DO gradient control and SRT control technologies, these three elements form a highly efficient synergistic mechanism, jointly solidifying the foundation for the stable operation of the short-cut nitrification system and further enhancing its shock resistance. It is precisely based on this synergistic control system that, through targeted technical design, this invention effectively solves the inherent defects of traditional short-cut nitrification processes in terms of system operational stability and shock resistance. Traditional short-cut nitrification processes are highly sensitive to fluctuations in parameters such as pH, DO, and temperature, and are prone to drift towards complete nitrification. However, this invention, through a combined technology package of "gradient DO + FA / pH synergistic control + biofilm enrichment," can maintain a long-term stable nitrite accumulation rate (NAR) above 85%, with a short recovery period after parameter fluctuations, ensuring the stability of the short-cut nitrification effect. In response to shock loads caused by a sudden increase in influent ammonia nitrogen concentration, nitrifying bacteria in traditional processes are easily inhibited by free ammonia (FA), leading to process instability. The intelligent control system of this invention can quickly initiate internal backflow dilution and pH adjustment measures when FA concentration exceeds the standard, controlling the FA concentration in the tank below the tolerance threshold of nitrifying bacteria, ensuring that the system is not affected by shocks and maintains stable operation.

[0058] Entering the S3 and secondary anoxic tank (A2) treatment stage, the wastewater treated by the primary aerobic tank (O1) is introduced into the secondary anoxic tank (A2 tank). This tank serves as a post-short-cut denitrification unit, and its core function is to further remove nitrate nitrogen and nitrite nitrogen from the wastewater through denitrification reaction, thereby improving the overall denitrification efficiency of the system.

[0059] During the operation of the secondary anoxic tank (A2 tank), the dissolved oxygen (DO) concentration in the tank is strictly controlled to be ≤0.5mg / L to maintain a stable anoxic environment and ensure the smooth progress of the denitrification reaction. The denitrification nitrogen removal rate is controlled between 0.03 and 0.05 kg NO3. - Within the range of -N (kgMLSS / d), the reaction process makes full use of the added carbon source and the residual carbon source carried by the effluent of the primary aerobic tank to achieve deep denitrification removal of nitrate nitrogen and nitrite nitrogen in the tank, ensuring that the total nitrogen removal effect meets the standards.

[0060] To ensure precise carbon source addition, avoid waste, and guarantee denitrification efficiency, an online total nitrogen (TN) analyzer is installed at the inlet of the secondary anoxic tank (A2 tank) to monitor the total nitrogen concentration (C) of the influent entering the A2 tank in real time. TN The amount of carbon source added is calculated according to the formula Q=k×C. TN Dynamic control is implemented, where Q is the amount of secondary exogenous carbon source added, k is the carbon source coefficient, and k ranges from 2.5 to 3.5 when methanol is used as the carbon source, and from 3.5 to 4.5 when sodium acetate is used as the carbon source. TNThe real-time total nitrogen concentration (mg / L) in the influent to tank A2 is used as the reference. Regarding carbon source dosing control in tank A2, the accuracy can be improved based on the optimized scheme using TN monitoring: parameter optimization, and simultaneous monitoring of TN and NH4. + -N, with difference C TN -C NH4+ More accurate characterization of denitrification substrate NO x This dynamic dosing method ensures a precise match between carbon source dosage and influent total nitrogen concentration, balancing denitrification efficiency and operational economy. To meet the carbon source requirements of the denitrification process and improve nitrogen removal efficiency and operational stability, different types of exogenous carbon sources can be flexibly selected based on actual water quality and operating conditions, and the dosing location can be optimized. Commonly used exogenous carbon sources include easily degradable organic carbon sources such as methanol, sodium acetate, ethanol, and glucose. Various carbon sources can be flexibly replaced, and the dosing coefficient k needs to be recalibrated according to their denitrification kinetic parameters after replacement. While ensuring denitrification efficiency, some carbon source dosing points can be adjusted to the middle or later part of the A1 tank according to the influent carbon source distribution, optimizing the rationality of carbon source dosing and improving carbon source utilization and denitrification stability.

[0061] After the secondary anoxic tank (A2) is completed, the wastewater enters the S4 and secondary aerobic tank (O2) treatment stage. The wastewater treated in the A2 tank is sent to the secondary aerobic tank (O2 tank), and the DO concentration in the tank is controlled at 2.0~2.5mg / L to ensure uniform mixing. The wastewater is further oxidized to remove residual ammonia nitrogen, nitrite nitrogen and organic pollutants, making up for the deficiencies of the primary aerobic tank treatment. This ensures that the effluent quality fully meets the preset standards and lays the foundation for subsequent sludge-water separation.

[0062] After the secondary aerobic tank (O2) is completed, the wastewater enters the S5 stage, which involves sludge-water separation and recirculation. The wastewater treated in the O2 tank is sent to the secondary sedimentation tank, where solid-liquid separation is achieved by a sludge scraper. The supernatant after separation can be directly discharged in compliance with standards or enter the advanced treatment stage. The sludge generated by sedimentation is returned to the primary anoxic tank (A1 tank) through the sludge return pipeline, and the sludge return ratio (R2) is controlled at 50%-100% to maintain the activity of microorganisms in the system. The excess sludge is discharged from the system through the excess sludge discharge pump. According to the instructions of the SRT intelligent control module, the excess sludge discharge flow rate is adjusted to ensure that the SRT is stable at 10-15 days, so as to achieve selective elution of NOB and consolidate the short-cut nitrification effect.

[0063] During system operation, SRT collaborative control is executed synchronously. The central intelligent control unit is based on the online monitoring of MLSS concentration and residual sludge concentration (X). WAS ) and excess sludge discharge flow (Q) wThe current sludge retention time is calculated in real time according to the formula, and the frequency of the excess sludge discharge pump or the valve opening is dynamically adjusted through a closed-loop control algorithm to keep the SRT stable within the target range of 10 to 15 days. This SRT range is higher than the generation time of AOB but shorter than the generation time of NOB, so that the faster-growing AOB can be retained and enriched, while the slower-growing NOB is selectively eluted.

[0064] The core calculation formula is as follows: ; (Note: This formula ignores the trace amount of sludge lost with the effluent, as it has a negligible impact on the calculation results.) The system solves in reverse based on the set target SRT value and automatically adjusts Q. w This enables precise control.

[0065] In practical scenarios, to simplify control, a simplified control method based on the sludge return ratio (SRT) can be adopted. This method uses the real-time monitored sludge return ratio (R), system volume (V), and target SRT to directly calculate and control the excess sludge discharge (Qw). This method reduces the dependence on online sludge concentration meters and is easier to implement.

[0066] Simplified formula: ; The SRT control, together with the DO gradient regulation and FA / pH synergistic regulation in the O1 tank, forms a three-dimensional synergistic system. The three support and reinforce each other, further consolidating the AOB microbial community's dominance, ensuring long-term stability of short-cut nitrification, and avoiding the problem of short-cut nitrification drifting towards complete nitrification.

[0067] In addition, to further enhance the short-cut nitrification effect and shorten the system start-up cycle, exogenous AOB bacteria can be added to the O1 tank, or immobilized microbial packing can be used; this process can also be used as a pretreatment stage of the anaerobic ammonia oxidation process to improve the overall nitrogen removal efficiency; during system start-up or recovery, selective inhibitors such as hydroxylamine and sodium chlorate can be added to accelerate NOB inhibition and rapidly enrich AOB bacteria. The above optimization methods do not change the core process characteristics of this invention.

[0068] To verify the feasibility, practicality, and engineering application value of the process and system of this invention, a specific design demonstration is provided, taking a typical high-ammonia-nitrogen industrial wastewater treatment scenario (with coal chemical wastewater as the treatment target). All design parameters and calculation logic follow the process requirements and control strategies of this invention, as detailed below: Example: Demonstration of Coal Chemical Wastewater Treatment Process Design Based on the Method of the Invention 1. Design Basic Conditions Design capacity: Water treatment capacity Q = 3000 m³ 3 / d.

[0069] Influent water quality (referencing typical data from relevant industries): COD=850mg / L, BOD5=380mg / L, NH4 + -N=450mg / L, TN=550mg / L.

[0070] Effluent requirements: COD ≤ 200 mg / L, NH4 + -N≤35mg / L,TN≤35mg / L 2. Design and Calculation Specifications of Core Process Units 2.1 Hydrolysis and Acidification Pretreatment Unit Function: Converts some of the recalcitrant organic matter in wastewater into easily biodegradable volatile fatty acids, thus optimizing the carbon source form.

[0071] Design parameters: Hydraulic retention time (HRT) is set to 12 hours, and dissolved oxygen (DO) concentration is below 0.2 mg / L.

[0072] Pool volume calculation: V HR =Q×HRT=3000×(12 / 24)=1500m³.

[0073] 2.2 Design of the main denitrification and decarbonization process (AOAO) (1) Design of the primary anoxic tank (A1) Function: As a pre-denitrification tank, it bears the main denitrification load of the system.

[0074] Calculation formula: V A1 =(Q×ΔN) / (X×K de1 ).in: ΔN: The total nitrogen concentration removed from the A1 tank is set to 440 mg / L (i.e., the system TN is reduced from 550 mg / L to 110 mg / L).

[0075] X: The design mixed liquor sludge concentration (MLSS) is 4.0 kg / m³. 3 .

[0076] K de1 Using the optimized denitrification rate of this invention, 0.06 kg of NH4 was taken. + -N / (kgMLSS·d).

[0077] Design calculations: V A1 =(3000×0.44) / (4.0×0.06)=5500m 3 .

[0078] Corresponding hydraulic residence time (HRT) A1 =44 hours.

[0079] Supporting control: An online carbon-to-nitrogen ratio (C / N) monitoring and intelligent dosing device is designed and installed at the inlet of the A1 pool.

[0080] Internal reflux ratio: 300% (2) Design of the primary aerobic tank (O1) Function: As a short-cut nitrification reactor, it achieves and maintains efficient nitrite accumulation.

[0081] Design Model: V O1 =(Q×[NH4 + -N]) / NLR. Where: [NH4 + [-N]: Influent ammonia nitrogen concentration, 0.45 kg / m³ 3 .

[0082] NLR: Using the optimized ammonia nitrogen loading rate of this invention, take 0.2 kg NH4. + -N / (m 3 ·d).

[0083] Design calculations: V O1 =(3000×0.45) / 0.2=6750m 3 .

[0084] The corresponding hydraulic residence time HRTO1 = 53.6 hours.

[0085] Synergistic design for robust short-cut nitration: a. Physical zoning: Designed as a 4-cell series structure to achieve a dissolved oxygen gradient along the water flow direction (design value: 1.1→0.8→0.7→0.6mg / L).

[0086] b. Dynamically optimized FA and pH synergistic control After mixed liquor and sludge recirculation, the ammonia nitrogen concentration at the inlet of the primary O tank is approximately 100 mg / L. Under these conditions, the core of the intelligent control system is not a fixed single FA or pH value, but rather an optimization objective that aims to minimize operating costs while ensuring short-range nitrification stability, dynamically solving for the optimal combination of FA and pH.

[0087] The system's built-in optimization module executes the following differentiated strategies based on real-time water temperature and inlet water load: 1. Winter Low Temperature (-10℃) Strategy: The goal is to ensure basic inhibition efficiency. The system maintains the FA concentration within the effective inhibition limit range of 3~5 mg / L, and dynamically adjusts the pH to stabilize it at 7.8~8.0. This strategy avoids excessive alkalinity consumption at low temperatures in pursuit of high FA, achieving stable operation at the lowest cost under low temperature conditions.

[0088] 2. Spring and Autumn Normal Temperature (-20℃) Strategy: The goal is to achieve the best cost-effectiveness balance. The system optimizes the FA concentration within the highly effective inhibition range of 5~8 mg / L and precisely controls the pH within the conventional economic range of 7.6~7.8. Under these conditions, the system maximizes process performance with minimal alkalinity addition cost.

[0089] 3. Summer High Temperature (-30℃) Strategy: The objective shifts to risk prevention and emergency economic efficiency. To prevent excessive FA accumulation and inhibition of AOB (Active Biological Occurrence), the system sets the upper limit for FA monitoring at 8~12 mg / L and strictly limits the pH to 7.4~7.6. When FA is predicted to exceed the safe range, the system prioritizes executing the emergency command to "reduce alkali dosage and increase the internal reflux ratio (R1)". This strategy utilizes the system's inherent hydraulic dilution capacity to quickly and cost-effectively suppress FA peaks, making it the most economical safety assurance measure under high-temperature conditions.

[0090] Through the above-mentioned dynamic settings based on multi-objective optimization (stability, economy), the control system of the present invention achieves an intelligent upgrade from "fixed parameter" operation to "dynamic adjustment", which reduces the annual operating cost while ensuring the core stability of the process.

[0091] c. Bioenrichment: Design and add fixed biofilm packing material with a filling rate of 30% to enrich ammonia-oxidizing bacteria.

[0092] d. Operating parameters: The designed sludge retention time (SRT) of the system is 12 ± 2 days.

[0093] (3) Design of the secondary anoxic tank (A2) and the secondary aerobic tank (O2) A2 tank function: to perform deep denitrification to ensure that the total nitrogen in the effluent meets the standards.

[0094] Design calculation: using formula V A2 =(Q×ΔN A2 ) / (X×K de2 ), where K de2 Taking 0.04 kgN / (kgMLSS·d), V is calculated. A2 =1406.25m 3 HRT A2 =11.25 hours.

[0095] O2 pool function: to further oxidize residual pollutants and ensure overall stable effluent quality.

[0096] Design parameters: Design DO is 2.0 mg / L, HRT is 4.8 hours, and pool volume is 600 m³. 3 .

[0097] Sludge return ratio: 100%.

[0098] Although the illustrative specific embodiments of this application have been described above to enable those skilled in the art to understand this application, this application is not limited to the scope of the specific embodiments. For those skilled in the art, all applications utilizing the concept of this application are protected as long as various variations are within the spirit and scope of this application as defined and determined by the appended claims.

Claims

1. A modified multi-stage AO coupled high ammonia nitrogen wastewater treatment process, characterized in that, Includes the following steps: S1, Primary Anoxic Treatment: Wastewater is introduced into the primary anoxic tank, and mixed liquor from the primary aerobic tank is introduced at the same time, with the reflux ratio controlled; under low oxygen conditions, the carbon source in the wastewater is used to complete the denitrification reaction, and the carbon-nitrogen ratio in the tank is monitored and adjusted online in real time. S2, Primary aerobic treatment: The wastewater after primary anoxic treatment is sent to the primary aerobic tank, and the nitrification reaction is controlled in the short-cut nitrification stage by a four-in-one synergistic control system. The four-in-one synergistic regulation system includes: DO gradient regulation along the water flow direction, FA / pH synergistic regulation, biofilm enrichment, and system sludge retention time control; creating a competitive spatial environment for ammonia-oxidizing bacteria (AOB) through gradient DO regulation; selectively inhibiting the activity of nitrite-oxidizing bacteria (NOB) through FA / pH linkage regulation; providing attachment and growth sites and shock protection for ammonia-oxidizing bacteria (AOB) through biofilm enrichment; and selectively eluting NOB and consolidating the AOB community dominance through system sludge retention time (SRT) control. S3, Secondary anoxic treatment: The wastewater treated in the primary aerobic tank is introduced into the secondary anoxic tank. Under anoxic conditions, carbon sources are used to further remove nitrate nitrogen and nitrite nitrogen from the wastewater. The amount of external carbon source added is monitored and adjusted online. S4. Secondary aerobic treatment: The wastewater after secondary anoxic treatment is sent to the secondary aerobic tank, and the DO concentration in the tank is controlled to reach the preset aerobic standard to further oxidize and remove residual pollutants in the wastewater. S5. Sludge-water separation and return treatment: The wastewater after secondary aerobic treatment is sent to the secondary sedimentation tank for solid-liquid separation. The supernatant after separation can be directly discharged in compliance with standards or enter the advanced treatment stage. Part of the sludge generated by sedimentation is returned to the primary anoxic tank to maintain the activity of microorganisms in the system, and the remaining sludge is discharged from the system.

2. The processing technology according to claim 1, characterized in that, Before step S1, there is also a hydrolysis acidification pretreatment step: after adjusting the pH value of the wastewater, hydrolysis acidification is carried out to hydrolyze and acidify some of the recalcitrant organic matter in the wastewater into volatile fatty acids (VFA).

3. The improved multi-stage AO coupled high ammonia nitrogen wastewater treatment process according to claim 1, characterized in that, The S2 step is executed and regulated by a hierarchical collaborative control architecture: the field fast controller with built-in edge computing module is deployed on-site in the primary aerobic tank to achieve millisecond-level ultra-fast closed-loop control of free ammonia and pH; the central intelligent control unit is responsible for global parameter optimization and scheduling, and works with the field fast controller to form a fast-slow decoupled control closed loop.

4. The processing technology according to claim 1, characterized in that, The specific implementation method of DO gradient control in step S2 is as follows: the primary aerobic tank is divided into multiple series aeration zones along the water flow direction, and the DO concentration in each zone is independently controlled to form a gradient distribution that gradually changes along the water flow direction, adapting to the reaction requirements of different stages of short-cut nitrification; the multiple series aeration zones can be divided into four or three zones; when divided into four zones, the DO concentration control range of each zone is: Zone 1 0.9-1.2 mg / L, Zone 2 0.7-0.9 mg / L, Zone 3 0.6-0.8 mg / L, Zone 4 0.5-0.7 mg / L; when divided into three zones, the DO concentration control range of each zone is: Zone 1 0.9-1.1 mg / L, Zone 2 0.6-0.8 mg / L, Zone 3 0.5-0.7 mg / L.

5. The processing technology according to claim 1, characterized in that, In step S2, the FA / pH synergistic regulation utilizes the difference in tolerance of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) to free ammonia (FA). By adjusting the free ammonia concentration and pH value, FA is controlled within a concentration range that selectively inhibits NOB without inhibiting AOB, thereby selectively inhibiting NOB activity and promoting AOB growth and accumulation. The free ammonia (FA) concentration is determined in real time based on parameters including ammonia nitrogen concentration, pH value, and water temperature, and dynamically stabilized within the range of 5–15 mg / L. At low temperatures, it tends to be controlled at the lower limit of the range, and at high temperatures, it is strictly controlled at the upper limit of the range. To stabilize the free ammonia (FA) concentration, a three-stage regulation is implemented when free ammonia deviates from the target range: normal regulation corrects the free ammonia concentration by adjusting the alkalinity dosage; when free ammonia continues to exceed the standard, the alkalinity dosage is first reduced to lower the pH through nitrification acid production; if the pH still does not meet the standard after dropping to the safe lower limit, the internal reflux ratio is temporarily increased for hydraulic dilution; when the influent ammonia nitrogen exceeds the standard severely, wastewater storage or segmented influent is initiated; FA / pH The coordinated control adopts a field rapid controller and a central intelligent control unit to jointly execute FA / pH control; the central intelligent control unit calculates the dynamic FA target value online based on parameters including influent ammonia nitrogen, water temperature and alkalinity consumption cost and sends it to the field rapid controller; the field rapid controller performs closed-loop control of FA and pH based on real-time monitored pH, temperature and ammonia nitrogen data.

6. The improved multi-stage AO coupled high ammonia nitrogen wastewater treatment process according to claim 1, characterized in that, The biofilm enrichment in step S2 is achieved by setting up a biofilm carrier in the primary aerobic tank to provide space for ammonia-oxidizing bacteria (AOB) to attach and grow.

7. The processing technology according to claim 1, characterized in that, The sludge retention time control in step S2 is to control the system SRT within a range suitable for enriching ammonia-oxidizing bacteria (AOB) and eluting nitrite-oxidizing bacteria (NOB); by intelligently adjusting the amount of excess sludge discharged, and dynamically calculating the SRT based on the online monitoring of MLSS concentration, excess sludge concentration and sludge discharge flow rate, precise control of SRT is achieved.

8. The processing technology according to claim 1, characterized in that, In step S2, during the primary aerobic treatment, the ammonia nitrogen loading rate (NLR) is used as the core control parameter and kept within the preset optimization range to ensure efficient AOB metabolism, provide a stable environment for DO gradient regulation and FA / pH synergistic control, and ensure that the nitrite accumulation rate is maintained at or above the preset high value.

9. An improved multi-stage AO coupled high ammonia nitrogen wastewater treatment system, characterized in that, The system is used to implement the treatment process described in claims 1-8, including a core treatment unit connected in series along the water flow direction and a hierarchical collaborative control architecture. The core treatment unit includes at least a primary anoxic tank, a primary aerobic tank, a secondary anoxic tank, a secondary aerobic tank, and a secondary sedimentation tank. The hierarchical collaborative control architecture includes a field control unit and a central intelligent control unit. The field control unit is deployed next to the primary aerobic tank and is connected to the monitoring and execution equipment of the primary aerobic tank. The central intelligent control unit is connected to the field control unit and the monitoring and execution equipment of the entire system to achieve global parameter optimization and scheduling.

10. The processing system according to claim 9, characterized in that, The core treatment unit also includes a hydrolysis acidification tank connected in series upstream of the primary anoxic tank. This hydrolysis acidification tank is equipped with equipment for adjusting water quality, maintaining mixing, and monitoring the environment. The secondary sedimentation tank is equipped with sludge return, excess sludge discharge equipment, and monitoring instruments, all centrally controlled by an intelligent control unit to maintain stable sludge concentration. The primary aerobic tank has multi-level gradient aeration zones and corresponding monitoring and control equipment to create a dissolved oxygen gradient distribution adapted to short-cut nitrification requirements. The primary aerobic tank also features an optional rapid start-up auxiliary device for adding selective inhibitors during system startup or recovery to accelerate the enrichment of ammonia-oxidizing bacteria. The on-site control unit is connected to the primary... The aerobic tank's precise monitoring cluster and control actuator are connected to achieve coordinated control of free ammonia and pH, as well as emergency response. The precise monitoring cluster includes key parameter monitoring equipment for calculating free ammonia concentration, and the control actuator includes related equipment for pH adjustment, hydraulic dilution, and aeration control. The central intelligent control unit has multiple built-in functional control modules, corresponding to various coordinated control requirements of short-cut nitrification in the primary aerobic tank, carbon source addition, reflux ratio control, and sludge retention time control. The functional control modules include at least a sludge retention time calculation and control module, a dissolved oxygen gradient control module, a free ammonia and pH coordinated control module, and an ammonia nitrogen loading rate control module.

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