Fuzzy Control Method and System for Wastewater Treatment Lines in Small Towns

Abstract

The present invention discloses a fuzzy control method and system for a sewage treatment line in a small town, which belongs to the field of sewage treatment. The method generates a one-day water inlet plan for a biochemical pool according to the historical liquid level data of the regulating tank. During the water inlet period of the water inlet plan, water is inletted into the biochemical pool, and the end of the aerobic pool is dosed according to the preset dosage, and the aerobic pool is aerated according to the theoretical aeration time. The present invention changes the continuous flow into a batch treatment by means of regulation and control, and limits the dosage and aeration volume during each treatment, which is beneficial to reducing drug consumption and power consumption; fuzzy control is adopted to adapt to batch treatment; and the buffering effect of the regulating tank on the biochemical pool is combined to adjust the water inflow of the small town, which is sometimes more and sometimes less in a day, into a more regular water inflow period-stop period cycle, which is beneficial to the stability of the effluent quality; the limited aeration volume plus the setting of the stop period is beneficial to reduce the impact on biological phosphorus removal and nitrogen removal under the oxygen-rich state, and make full use of the carbon source in the sewage.

Description

Technical Field

[0001] The invention relates to a fuzzy control method and system for a small town sewage treatment line, belonging to the field of sewage treatment. Background Art

[0002] At present, most sewage treatment lines use AAO process to remove organic matter, nitrogen and phosphorus from sewage. The AAO process mainly includes three stages: anaerobic zone, anoxic zone and aerobic zone. Figure 1 As shown, sewage enters the regulating tank through the water collection well and the grit chamber. The water collection well is used to collect and temporarily store sewage; the grit chamber is used to remove larger inorganic particles in sewage, such as sand and sediment; the regulating tank is equivalent to the water storage tank before AAO treatment, which reduces the impact of peak load on the biochemical tank (the general term for anaerobic tank, anoxic tank, and aerobic tank) by homogenizing water quality and flow. Then the regulating tank feeds water to the biochemical tank, and the sewage will pass through the anaerobic tank, anoxic tank, aerobic tank and secondary sedimentation tank. In the aerobic tank, nitrifying bacteria convert ammonia nitrogen in sewage into nitrate. The sewage containing nitrate in the aerobic tank is returned to the anoxic tank. In the anoxic tank, denitrifying bacteria convert the nitrate brought by the internal return flow into nitrogen gas and discharge it into the atmosphere, thereby achieving denitrification; in the anaerobic tank, polyphosphate bacteria release phosphorus and absorb easily degradable organic matter such as low-level fatty acids. In the aerobic tank, polyphosphate bacteria absorb phosphorus in excess and form sludge in the secondary sedimentation tank. Part of the sludge is discharged to remove phosphorus, and part of the sludge is returned to the anaerobic tank to ensure the microbial concentration in the biochemical tank. The supernatant of the secondary sedimentation tank continues to undergo deep treatment (such as activated carbon adsorption) and disinfection to meet the effluent standards. Biological phosphorus removal has certain limitations, and chemical phosphorus removal agents are usually added at the end of the aerobic tank (for example, at the outlet water of the aerobic tank or 1 meter away from the outlet of the aerobic tank) to keep the total phosphorus in the effluent from exceeding the standard.

[0003] In order to strictly control the total phosphorus, total nitrogen, ammonia nitrogen, and COD (chemical oxygen demand) of the effluent and minimize the cost (power consumption, drug consumption, etc.), the key control parameters are: the water inflow from the regulating pool to the biochemical pool, the aeration volume of the aerobic pool by the blower, and the dosage of the phosphorus removal agent added to the end of the aerobic pool by the dosing pump. Thanks to the development of information technology, the control of these parameters in large-scale sewage treatment plants can be automated, and these parameters can be accurately controlled through feedforward, feedback and other means, which can not only keep the effluent qualified, but also avoid excessive dosing and excessive aeration.

[0004] However, there are two foundations for large sewage treatment plants to achieve this kind of precise control that small town sewage treatment plants do not have. First, large sewage treatment plants receive a large amount of sewage, which can keep the sewage treatment line running continuously; while small town sewage treatment plants have to stop water intake during the period when they receive less sewage, which cannot meet the conditions of feedforward and feedback. The feedforward and feedback of large sewage treatment plants differ by about 20 hours. If the water intake is stopped, the feedforward regulation will be lost in the middle of the operation; if the water intake is stopped for a period of time and then restarted, the feedback regulation will be missing. Second, the precise control of large sewage treatment plants depends on many sensors. Small towns have relatively less investment in the construction and operation of sewage treatment plants. Small town sewage treatment plants are small in scale (the treatment capacity of small town sewage treatment plants is at the level of thousands of tons per day, while that of large sewage treatment plants is at the level of tens of thousands of tons per day), and the hardware facilities are not as rich as those of large sewage treatment plants.

[0005] Therefore, small town sewage treatment plants usually rely on experience to adjust key parameters such as the water inflow from the regulating tank to the biochemical tank, the aeration volume of the aerobic tank by the blower, and the amount of phosphorus removal agent added by the dosing pump to the end of the aerobic tank. Automated control is the general trend of the times. How to achieve automated control without satisfying precise control has become an urgent problem to be solved in this field. Summary of the invention

[0006] In order to overcome the deficiencies of the prior art, the present invention provides a fuzzy control method and system for a sewage treatment line in a small town, which can realize automatic control under the condition of intermittent water inflow.

[0007] The technical solution adopted by the present invention to solve its technical problem is:

[0008] In the first aspect, the present application provides a fuzzy control method for a small town sewage treatment line, which is applicable to the AAO process, and the method includes: obtaining historical liquid level data of the regulating tank, generating a one-day water inflow plan for the biochemical tank according to the historical liquid level data of the regulating tank, and the water inflow plan includes multiple alternating water inflow periods and stop periods; during the water inflow period, water is introduced into the biochemical tank, and after a preset flow time is delayed from the starting point of the water inflow period, the end of the aerobic tank is added with a preset dosage, and the aerobic tank is aerated according to the theoretical aeration time.

[0009] The present application provides a fuzzy control method for small town sewage treatment lines, which abandons the idea of ​​continuous treatment and multi-parameter monitoring, and adjusts the original full-process, complex, and lagging automatic control to a more regular water inlet period-stop period cycle, and establishes a control technology that focuses on operating logic. It is conducive to adapting to the characteristics of small town water inflow that is relatively regular on a daily basis and irregular on an hourly basis, and can ensure that the effluent quality is stable and meets the standards with high efficiency and low consumption.

[0010] When changing continuous flow to batch treatment, attention should be paid to the water inflow time of a single water inflow period and the stop time of a single stop period. If the stop period is too short, the carbon source in the sewage cannot be well utilized; if the stop period is too long, the bacterial activity in the biochemical pool is easily reduced; if the water inflow period is too long, the amount of water that can be inflowed in the next water inflow period may be reduced, resulting in large differences in the length of different water inflow periods in a day, which is not conducive to controlling the stability of water quality.

[0011] Optionally, the water inflow period includes a peak period and a zero week, and the step of generating a one-day water inflow plan for the biochemical pool according to the historical liquid level data of the regulating pool includes:

[0012] The continuous period in which the liquid level in the historical liquid level data of the regulating tank is above 65% of the volume of the regulating tank and maintained for more than 1 hour is classified as the peak period in the water inflow plan;

[0013] A zero week is inserted into the time period immediately adjacent to the peak period or the time period staggered with the peak period, and the remaining time period is a stop period, so that the duration of a single water inflow period containing the zero week is less than the maximum continuous water inflow time, and the duration of a single stop period is less than the maximum static time.

[0014] The significance of designing the zero week is to prevent the biochemical system from being out of control for too long, while consuming sporadic water inflows during some periods, so that the duration of each water inflow period will not differ too much. Preferably, the duration of a single water inflow period that only includes the zero week is more than 1 hour.

[0015] Optionally, the maximum continuous water inflow time is equal to the volume of the regulating tank multiplied by 0.8 and then divided by the rated flow of the regulating tank lift pump.

[0016] Optionally, the step of determining the maximum static time includes:

[0017] When the sewage treatment line is operating at full capacity, the water supply to the biochemical pool, aeration, internal recirculation and dosing are suddenly stopped. Under the condition of a constant external recirculation volume, the time required for the ammonia nitrogen value of the effluent from the aerobic pool to drop to 2 mg / L is set as the maximum standing time.

[0018] Optionally, the historical liquid level data of the regulating tank is liquid level data at the same time in the previous 3 to 10 days, and the step of dividing the continuous period in which the liquid level in the historical liquid level data of the regulating tank is above 65% of the volume of the regulating tank and maintained for more than 1 hour as the peak period in the water inflow plan includes:

[0019] According to the historical liquid level data of the regulating tank, the time when the liquid level of the regulating tank is above 65% and the frequency of meeting this requirement is above 50% in multiple days is set as the peak time;

[0020] The peak moments that are continuous and have a duration of more than 1 hour are classified as the peak period in the water intake plan.

[0021] Optionally, the step of determining the theoretical aeration time includes:

[0022] The initial ammonia nitrogen value of the biochemical pool influent is obtained, and the theoretical aeration time corresponding to the current influent period is calculated according to the target ammonia nitrogen value of the biochemical pool effluent, the rated air volume of the blower used for aeration, the influent volume of the current influent period and the initial ammonia nitrogen value.

[0023] The target ammonia nitrogen value may be, for example, the standard value of the effluent, 0.8 times the standard value of the effluent, etc. The water inflow during the current inflow period can be simply calculated from the duration of the inflow period and the rated flow rate of the regulating tank lift pump.

[0024] Optionally, the step of determining the preset dosage includes:

[0025] The sewage treatment line is operated at full load except for the dosing pump, and dosing is performed at different dosing flow rates. The total phosphorus value of the total effluent is measured, and the smallest dosing flow rate corresponding to the total phosphorus value that does not exceed the standard is recorded as the preset flow rate. The preset dosing amount is equal to the preset flow rate multiplied by the duration of the water inlet period.

[0026] Optionally, the opening and closing of the internal recirculation is synchronized with the opening and closing of the blower, and when the internal recirculation is started:

[0027] If the effluent from the secondary sedimentation tank meets the requirements of total nitrogen value <12mg / L and ammonia nitrogen value <2mg / L, the internal recirculation will be operated at 50% of its load;

[0028] If the total nitrogen value is not less than 12 mg / L and the ammonia nitrogen value is less than 2 mg / L, the internal reflux will operate at full load. On this basis, if the total nitrogen value of the total effluent is greater than 12 mg / L and the total nitrogen value of the total effluent minus the total effluent ammonia nitrogen value is greater than 10 mg / L, the addition of carbon source will be executed or reminded.

[0029] In the second aspect, the present application provides a fuzzy control system for a small town sewage treatment line, which includes a regulating tank, a biochemical tank and a secondary sedimentation tank in sequence according to the sewage flow direction. The biochemical tank adopts an AAO process, and the regulating tank is provided with a regulating tank lift pump for feeding water into the biochemical tank. The biochemical tank is provided with a blower for aerating the aerobic tank and a dosing pump for adding a treatment agent to the end of the aerobic tank, and also includes a controller, and the controller includes:

[0030] An acquisition module is used to obtain historical liquid level data of the regulating tank;

[0031] A scheduling module, used to generate a daily water inflow plan for the biochemical pool according to the historical liquid level data of the regulating pool; the water inflow plan includes a plurality of alternating water inflow periods and stop periods;

[0032] The execution module is used to control the lifting pump of the regulating tank to feed water into the biochemical tank during the water inlet period, and after delaying the preset flow time from the starting point of the water inlet period, control the dosing pump to add medicine to the last section of the aerobic tank according to the preset dosing amount, and control the blower to aerate the aerobic tank according to the theoretical aeration time.

[0033] Furthermore, the scheduling module is used to classify the continuous period in which the liquid level in the historical liquid level data of the regulating tank is continuously above 65% of the regulating tank volume and maintained for more than 1 hour as the peak period in the water inflow plan;

[0034] A zero week is inserted into the time period immediately adjacent to the peak period or the time period staggered with the peak period, and the remaining time period is a stop period, so that the duration of a single water inflow period containing the zero week is less than the maximum continuous water inflow time, and the duration of a single stop period is less than the maximum static time.

[0035] Furthermore, the scheduling module is used to set the time when the liquid level of the regulating tank meets the requirement of more than 65% and the frequency of meeting the requirement is more than 50% in multiple days as the peak time according to the historical liquid level data of the regulating tank;

[0036] The peak moments that are continuous and have a duration of more than 1 hour are classified as the peak period in the water intake plan.

[0037] Furthermore, the acquisition module is also used to obtain the initial ammonia nitrogen value of the biochemical pool influent;

[0038] The fuzzy control system of the small town sewage treatment line also includes a calculation module, which is used to calculate the theoretical aeration time corresponding to the current water inlet period based on the target ammonia nitrogen value of the biochemical pool effluent, the rated air volume of the blower used for aeration, the water inflow during the current water inlet period and the initial ammonia nitrogen value.

[0039] Furthermore, the acquisition module is also used to obtain the total nitrogen value of the secondary sedimentation tank effluent, the ammonia nitrogen value of the secondary sedimentation tank effluent, the total nitrogen value of the total effluent, and the ammonia nitrogen value of the total effluent;

[0040] The execution module is also used to control the opening and closing of the internal reflow and the opening and closing of the blower synchronously, and when the internal reflow is started:

[0041] If the effluent from the secondary sedimentation tank meets the requirements of total nitrogen value <12mg / L and ammonia nitrogen value <2mg / L, the internal recirculation will be operated at 50% of its load;

[0042] Otherwise, the internal reflux operates at full load; when the total effluent nitrogen value is greater than 12 mg / L and the total effluent nitrogen value minus the total effluent ammonia nitrogen value is greater than 10 mg / L, the addition of carbon source is executed or reminded.

[0043] The beneficial effects of the present invention are as follows: the present invention changes the continuous flow into batch treatment by means of regulation and control, and limits the dosage and aeration volume in each treatment, which is beneficial to reducing the drug consumption and power consumption; and adopts fuzzy control to minimize the real-time feedforward and feedback regulation to adapt to the batch treatment; and also combines the buffering effect of the regulating tank on the biochemical tank to adjust the water inflow of small towns, which is sometimes more and sometimes less during the day, into a more regular water inlet period-stop period cycle, which is beneficial to the stability of the effluent quality; the limited aeration volume plus the setting of the stop period are beneficial to reducing the impact on biological phosphorus removal and nitrogen removal under the oxygen-rich state, and making full use of the carbon source contained in the sewage.

[0044] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or understood by practicing the present application. The purpose and other advantages of the present application can be realized and obtained by the structures particularly pointed out in the written description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a schematic diagram of the structure of a general AAO sewage treatment line.

[0046] Figure 2 This is one of the charts showing the water level status and scheduling results of the regulating tank of the pilot sewage treatment plant in the first 8 days.

[0047] Figure 3 This is the water level status and scheduling results of the pilot sewage treatment plant in the regulating tank in the first 8 days

[0048] Figure 4 This is a graph of experimental results during the exploration of the preset dosage.

[0049] Figure 5 This is the water output data chart for March after the pilot project was put into full automatic operation.

[0050] Figure 6 This is the water output data chart for April after the pilot project was put into full automatic operation. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution of the embodiments of the present disclosure is clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] It should be understood that, under the premise of no conflict, any and all embodiments of the present invention can be combined with the technical features in any other embodiment or multiple other embodiments to obtain another embodiment. The present invention includes such a combination to obtain another embodiment.

[0053] Unless otherwise specified, all technical and scientific terms used herein have the standard meaning in the field to which the claimed subject matter belongs. If there are multiple definitions for a term, the definition herein shall prevail.

[0054] In view of the relatively simple equipment, insufficient and regular water inflow of sewage treatment plants in small towns, the embodiment of the present application establishes an automatic operation mode of fuzzy process control, applies the process control principles and operation methods to small-scale urban sewage treatment plants from the source, and achieves the goal of ensuring stable effluent compliance and reducing the difficulty of process control under the conditions of limited capital investment and insufficient technical force.

[0055] The present application embodiment provides a fuzzy control method for a small town sewage treatment line, which is applicable to the AAO process, for example, Figure 1 The sewage treatment line shown in the figure. The sewage enters the regulating tank through the water collection well and the sand settling tank, and then the regulating tank feeds the biochemical tank. The sewage will pass through the anaerobic tank, the anoxic tank, the aerobic tank and the secondary sedimentation tank. Sludge is formed in the secondary sedimentation tank, part of which is discharged and part of which is returned to the anaerobic tank. The supernatant of the secondary sedimentation tank is further treated and disinfected before being discharged.

[0056] The method comprises: obtaining historical liquid level data of the regulating tank, generating a one-day water inflow plan for the biochemical tank according to the historical liquid level data of the regulating tank, wherein the water inflow plan comprises a plurality of water inflow periods and stop periods which alternate with each other; during the water inflow period, water is inflowed into the biochemical tank, and after a preset flow time is delayed at the starting point of the water inflow period, a preset dosage is added to the end of the aerobic tank, and the aerobic tank is aerated according to the theoretical aeration time.

[0057] Among them, the "water inflow" mentioned in the water inflow plan and water inflow period refers to the water inflow from the regulating tank to the biochemical tank. Aeration refers to the use of a blower to transport oxygen-containing gas (in most cases, air) to the aerobic tank. The internal reflow in the AAO process refers to the mixed liquid at the end of the aerobic tank returning to the front end of the anoxic tank. The external reflow refers to the sludge at the bottom of the secondary sedimentation tank returning to the sludge storage tank ( Figure 1 The sludge storage tank pumps the sludge to the front end of the anaerobic tank. Dosing refers to adding the phosphorus removal agent to the end of the aerobic tank. Considering the scale of the sewage treatment plant in small towns, the preset flow time can be 1.5 hours.

[0058] The embodiment of the present application is based on fuzzy intelligent control technology of sewage treatment plant process. It aims at small-scale urban sewage treatment plants with few instrument parameters, few frequency conversion facilities and equipment, weak technical analysis and extensive control. It establishes a non-fine and nonlinear control technology that focuses on operation logic, and realizes linkage automation of water intake, aeration, backflow, dosing and other processes according to a certain logic, thereby improving effluent stability and reducing electrochemical costs.

[0059] This technology can be generally understood as follows: for small town sewage treatment plants, the daily and seasonal water inflow is relatively regular and the composition is relatively stable; in terms of hours, there are peak water inflow periods and periods with little or even no water. If it is operated continuously, it will obviously consume too much electricity and medicine; if the amount of water entering the biochemical pool, the amount of aeration, the amount of dosing, the amount of return flow, etc. are determined according to the actual situation when water comes in, it will be too dependent on experienced technicians, because the existing automatic control system is not suitable for intermittent working conditions. Therefore, the water in a day is simply divided into multiple rounds of treatment, and the dosing amount and aeration amount of each round of treatment are controlled to be roughly excessive, ensuring that the effluent meets the standard while the power consumption and drug consumption are low. "Approximately excessive" means that there is no need to calculate the dosage and aeration volume as accurately as in large-scale sewage treatment plants. The method of calculating the dosage and aeration volume can consider fewer parameters and rely on fewer sensors. The resulting dosage and aeration volume only need to make the effluent qualified. It is not necessary to require the highest efficiency, because switching to batch treatment is more chemical and electricity-saving than continuous flow. On this basis, automated control of small town sewage treatment plants has also been achieved.

[0060] The target of the pilot transformation is a sewage treatment plant in Luogang Town, Xingning City, with a design capacity of 2,500 tons / day. It adopts AAO+rotating disc filter+pipeline UV disinfection technology, and the effluent complies with Class A emission standards. After summarizing the total effluent flow and load rate data of the plant from January to May 2023, the average daily effluent flow is 1,475 tons / day and the load rate is 59.03%, which is representative of small town sewage treatment plants.

[0061] The drainage and water filling plan must first clarify the maximum static time and the maximum water filling time.

[0062] The steps for determining the limit standing time include: when the sewage treatment line is operating at full capacity, suddenly stop the water inlet to the biochemical pool, stop aeration, stop internal reflux, and stop adding drugs. Under the condition of constant external reflux, the time required for the ammonia nitrogen detection value of the aerobic pool effluent to drop to 2 mg / L is set as the limit standing time. The limit standing time needs to be revised regularly, for example, once a month. In this experiment, the indicators at the end of the aerobic pool were tested. After stopping the water inlet and standing for 2 hours, the ammonia nitrogen concentration was 1.98 mg / L, COD, total phosphorus, total nitrogen, and ammonia nitrogen (only measured during correction, not all real-time monitoring is required during future operation) all dropped to the optimal value, the total phosphorus concentration was 1.05 mg / L, the orthophosphate concentration was 0.37 mg / L, the total nitrogen concentration was 10.40 mg / L, and the nitrate nitrogen concentration was 3.73 mg / L. After continuing to stand for 3h, 4h, and 5h, COD remained almost unchanged, orthophosphate decreased slightly, and nitrate nitrogen gradually decreased, but total phosphorus, total nitrogen, and ammonia nitrogen all gradually increased and began to affect the effluent quality. Based on this, the maximum standing time was determined to be 2 hours.

[0063] The maximum water inflow time is related to the volume of the regulating pool, the rated flow of the regulating pool lifting pump, and also has a certain relationship with the conditions for determining the peak period. In this pilot, the maximum continuous water inflow time is equal to the volume of the regulating pool multiplied by 0.8 and then divided by the rated flow of the regulating pool lifting pump, which is calculated to be 3 hours.

[0064] Before the improvement, the sump lift pump of the pilot sewage treatment plant operated automatically and continuously according to the liquid level gauge of the sump. Whenever the liquid level reached 80%, it was automatically pumped to the biochemical pool (via the grit tank and regulating pool). The pump stopped pumping water to the biochemical pool when the liquid level was lower than 20%. The varying amounts of water inflow caused great trouble to the decision-making on aeration volume, dosage, internal reflux, and external reflux.

[0065] This improvement divides a day into multiple moments of 15 minutes each, obtains the liquid level of the regulating pool at each moment, and performs batch water inflow. The historical liquid level data of the regulating pool for a total of 8 days from May 24, 2023 to May 31, 2023 was obtained. There are too many values ​​to list all of them, please refer to Figure 2 and Figure 3 ( Figure 2 and Figure 3 In fact, it is the same table, but it is cut into two parts due to the page size limit. Figure 2 and Figure 3 It is easier to understand when spliced ​​together), simplify these data into reaching 65% of the volume of the regulating tank and not reaching 65% of the volume. The 0 in the moment represents the first moment, 15 represents the second moment, 30 represents the third moment, and 45 represents the fourth moment.

[0066] The frequency of the water level in the regulating pond reaching 65% at the same time on different days is counted. If the water level is above 65% on more than 50% of the days at a certain moment, then that moment is set as the peak moment. If there are more than 4 consecutive peak moments (i.e., consecutive periods lasting more than 1 hour), then that period is set as the peak period of the water inflow plan on June 1.

[0067] Peak time Figure 2 and Figure 3 The water intake plan for June 1 is shown in Figures 2 and Figure 3 As shown in row B in . Although 12:00 and 23:00 are peak hours, there is no adjacent peak hour to form a continuous period of more than 1 hour, so in row B, they are not considered as peak periods. The peak periods obtained are from 7:15 to 10:30 (195 minutes), from 12:45 to 14:15 (105 minutes), and from 17:45 to 20:15 (165 minutes). Then insert zero weeks in the period immediately following the peak period (such as 17:35) or the period staggered from the peak period (such as 3:25 to 5:15), and the remaining period is the stop period, as shown in row B. Figure 2 and Figure 3 As shown in row B, the stop period cannot be longer than two hours and the water intake period including zero weeks cannot be longer than three hours.

[0068] When scheduling the water inlet period on June 2, the liquid level data from May 25 to June 1 will be used as the historical liquid level data of the regulating tank, so that the system can automatically schedule operation.

[0069] Next, we discuss the dosage. Except for the dosing pump, the sewage treatment line is operated at full load, and the dosing is performed at different dosing flow rates. The total phosphorus value of the total effluent is measured, and the smallest dosing flow rate corresponding to the total phosphorus value that does not exceed the standard is recorded as the preset flow rate. The preset dosage is equal to the preset flow rate multiplied by the length of the water inlet period. Similarly, the preset dosage needs to be revised regularly, for example, once a month.

[0070] In this experiment, the experiment was conducted at 0%, 30%, 50%, and 80% of the full load flow of the dosing pump. 0% means that the water quality is directly measured without adding drugs. Samples were taken at three points, namely the end of the aerobic tank, the middle of the secondary sedimentation tank, and the effluent of the secondary sedimentation tank, to test the total phosphorus value and phosphate concentration. The results are as follows: Figure 4 It is shown that both 50% and 80% of the full load flow of the dosing pump can make the total phosphorus value of the secondary sedimentation tank meet the standard, and the 50% dosing flow is selected.

[0071] Sequential batch treatment provides a good opportunity: when the actual oxygen demand exceeds the supply, the blower can be stopped to temporarily change the original aerobic pool functional area into an anoxic pool functional area, reducing the impact on biological phosphorus removal and nitrogen removal under oxygen-rich conditions and achieving stability in process operation control and management.

[0072] Therefore, it is necessary to explore the theoretical aeration time: obtain the initial ammonia nitrogen value of the biochemical pool inlet water, and calculate the theoretical aeration time corresponding to the current water inlet period based on the target ammonia nitrogen value of the biochemical pool effluent, the rated air volume of the blower used for aeration, the water inlet volume of the current water inlet period, and the initial ammonia nitrogen value.

[0073] It can be set as follows:

[0074] .

[0075] in:

[0076] T——theoretical aeration time;

[0077] 0.001——Nitrogen oxygen demand coefficient:

[0078] 4.57 – Nitrogen to oxygen ratio;

[0079] Q——water inflow during the current inflow period;

[0080] N 进 ——initial ammonia nitrogen value;

[0081] N0——target ammonia nitrogen value;

[0082] 0.28——oxygen conversion coefficient;

[0083] 0.25——oxygen utilization rate;

[0084] S——Rated air volume of the blower used for aeration;

[0085] 0.30——The proportion of blower air output.

[0086] This process does not involve post-feedback, and only requires knowing the initial ammonia nitrogen value of the biochemical pool influent, which is suitable for sequencing batch treatment.

[0087] In conjunction with the above methods, a fuzzy control system for the small town sewage treatment line was improved in the pilot project. According to the sewage flow direction, it includes an equalization tank, a biochemical tank and a secondary sedimentation tank. The biochemical tank adopts the AAO process. The equalization tank is equipped with an equalization tank lifting pump for feeding water into the biochemical tank. The biochemical tank is equipped with a blower for aerating the aerobic tank and a dosing pump for adding treatment agents to the end of the aerobic tank. It also includes a controller.

[0088] The controller includes:

[0089] The acquisition module is used to obtain the historical liquid level data of the regulating tank; it is also used to obtain the initial ammonia nitrogen value of the influent of the biochemical pool.

[0090] The scheduling module is used to set the peak time as the time when the liquid level of the regulating pool meets the requirement of more than 65% and the frequency of meeting this requirement is more than 50% in multiple days according to the historical liquid level data of the regulating pool;

[0091] The continuous peak moments with a duration of more than 1 hour are classified as the peak period in the water intake plan;

[0092] Zero weeks are inserted into the period immediately adjacent to the peak period or the period staggered with the peak period, and the remaining period is the stop period, so that the duration of a single water inflow period is less than the maximum continuous water inflow period, and the duration of a single stop period is less than the maximum static period.

[0093] The execution module is used to control the lifting pump of the regulating tank to feed water into the biochemical tank during the water inlet period, and after delaying the preset flow time at the starting point of the water inlet period, control the dosing pump to add medicine to the end of the aerobic tank according to the preset dosing amount, and control the blower to aerate the aerobic tank according to the theoretical aeration time;

[0094] It is also used to control the opening and closing of the internal recirculation and the opening and closing of the blower synchronously, and when the internal recirculation is started:

[0095] If the effluent from the secondary sedimentation tank meets the requirements of total nitrogen value <12mg / L and ammonia nitrogen value <2mg / L, the internal recirculation will be operated at 50% of its load;

[0096] Otherwise, the internal reflux operates at full load; when the total effluent nitrogen value is greater than 12 mg / L and the total effluent nitrogen value minus the total effluent ammonia nitrogen value is greater than 10 mg / L, the addition of carbon source is executed or reminded.

[0097] So far, except for the periodic corrections that require manual experiments, the rest of the time can be automatically run. During the automatic operation, the reference parameters only involve the initial ammonia nitrogen value of the biochemical pool inlet, the total nitrogen value of the secondary sedimentation tank effluent, the ammonia nitrogen value of the secondary sedimentation tank effluent, the liquid level of the secondary sedimentation tank, the liquid level of the regulating tank, the total effluent ammonia nitrogen value, and the total effluent total nitrogen value. Among them, the total effluent index and liquid level meter are available in every sewage treatment line. The hardware requirements for new projects are low, the detection parameters are few, there is no correlation between feedforward and feedback, and each judgment is made separately.

[0098] From January 2022 to May 2023, the pilot project used the original process operation control management method, with an average monthly electricity consumption of 28,900 kWh and an electricity consumption of 0.62 kWh / ton of water. From June 2023 to February 2024, the small-scale urban sewage treatment plant fuzzy process control technology was implemented with manual assistance, with an average monthly electricity consumption of 19,900 kWh and an electricity consumption of 0.47 kWh / ton of water. From March 2024 to date, the small-scale urban sewage treatment plant fuzzy process control technology has been fully automatically operated, with an average monthly electricity consumption of 16,000 kWh and an electricity consumption of 0.40 kWh / ton of water. The energy-saving and consumption-reduction target was achieved with a 30% reduction in electricity consumption and a 20% reduction in electricity consumption. The monthly effluent quality data can achieve a stable and standard working state except for the abnormal state detected by the online monitoring instrument.

[0099] The water quality of the pilot project in March 2024 will be Figure 5As shown in Figure 2, the water quality of the pilot project in April 2024 will be as follows: Figure 6 The four indicators measured are total phosphorus, COD, ammonia nitrogen and total nitrogen, and the sampling points are all the total effluent of the sewage treatment line (the effluent after disinfection, the same throughout the text). Figure 5 and Figure 6 In the table, the horizontal axis is the date, and the vertical axis is in mg / L. The COD value is on the left vertical axis, and the total phosphorus, total nitrogen, and ammonia nitrogen are on the right vertical axis. This proves that after full automatic operation, the effluent can still be kept qualified on the basis of reducing power consumption and drug consumption.

[0100] In the description of this specification, the description with reference to the terms "one embodiment", "certain embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0101] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A fuzzy control method for a sewage treatment line in a small town, suitable for the AAO process, wherein the biochemical pool is an anaerobic pool, an anoxic pool and an aerobic pool connected in sequence, characterized in that: Acquire historical liquid level data of the regulating pool, and generate a water inflow plan for the biochemical pool for one day according to the historical liquid level data of the regulating pool, wherein the water inflow plan includes a plurality of water inflow periods and stop periods that alternate in turn; during the water inflow period, water is inflowed into the biochemical pool, and after a preset flow time is delayed at the starting point of the water inflow period, the end section of the aerobic pool is dosed with a preset dosing amount, and the aerobic pool is aerated according to the theoretical aeration time; The water inflow period includes a peak period and a zero week, and the step of generating a one-day water inflow plan for the biochemical pool according to the historical liquid level data of the regulating pool includes: The continuous period in which the liquid level in the historical liquid level data of the regulating tank is above 65% of the volume of the regulating tank and maintained for more than 1 hour is classified as the peak period in the water inflow plan; A zero week is inserted into the period immediately adjacent to the peak period or the period staggered from the peak period, and the remaining period is a stop period, so that the duration of a single water inflow period containing the zero week is less than the maximum continuous water inflow duration, and the duration of a single stop period is less than the maximum static duration; The maximum continuous water inflow time is equal to the volume of the regulating tank multiplied by 0.8 and then divided by the rated flow rate of the regulating tank lift pump; The step of determining the limit static time comprises: When the sewage treatment line is operating at full capacity, the water supply to the biochemical pool, aeration, internal reflux, and dosing are suddenly stopped. Under the condition of a constant external reflux flow, the time required for the ammonia nitrogen value of the effluent from the aerobic pool to drop to 2 mg / L is set as the maximum static time; The historical liquid level data of the regulating tank is the liquid level data at the same time in the previous 3 to 10 days. The step of dividing the continuous period in which the liquid level in the historical liquid level data of the regulating tank is above 65% of the volume of the regulating tank and maintained for more than 1 hour as the peak period in the water inflow plan includes: According to the historical liquid level data of the regulating tank, the time when the liquid level of the regulating tank is above 65% and the frequency of meeting this requirement is above 50% in multiple days is set as the peak time; The peak moments that are continuous and have a duration of more than 1 hour are classified as the peak period in the water intake plan.

2. The fuzzy control method for a small town sewage treatment line according to claim 1 is characterized in that: The steps for determining the theoretical aeration time include: The initial ammonia nitrogen value of the biochemical pool influent is obtained, and the theoretical aeration time corresponding to the current influent period is calculated according to the target ammonia nitrogen value of the biochemical pool effluent, the rated air volume of the blower used for aeration, the influent volume of the current influent period and the initial ammonia nitrogen value.

3. The fuzzy control method for a small town sewage treatment line according to claim 1 is characterized in that: The step of determining the preset dosage comprises: The sewage treatment line is operated at full load except for the dosing pump, and dosing is performed at different dosing flow rates. The total phosphorus value of the total effluent is measured, and the smallest dosing flow rate corresponding to the total phosphorus value that does not exceed the standard is recorded as the preset flow rate. The preset dosing amount is equal to the preset flow rate multiplied by the duration of the water inlet period.

4. The fuzzy control method for a sewage treatment line in a small town according to claim 2 is characterized in that: The opening and closing of the internal recirculation is synchronized with the opening and closing of the blower, and when the internal recirculation is started: If the effluent from the secondary sedimentation tank meets the requirements of total nitrogen value <12mg / L and ammonia nitrogen value <2mg / L, the internal recirculation will be operated at 50% of its load; Otherwise, the internal reflux operates at full load; when the total effluent nitrogen value is greater than 12 mg / L and the total effluent nitrogen value minus the total effluent ammonia nitrogen value is greater than 10 mg / L, the addition of carbon source is executed or reminded.

5. A fuzzy control system for a sewage treatment line in a small town, adopting the fuzzy control method for a sewage treatment line in a small town as described in any one of claims 1 to 4, comprising a regulating tank, a biochemical tank and a secondary sedimentation tank in order according to the flow direction of sewage, the biochemical tank adopts the AAO process, the regulating tank is provided with a regulating tank lift pump for feeding water into the biochemical tank, the biochemical tank is provided with a blower for aerating the aerobic tank and a dosing pump for adding treatment agents to the end of the aerobic tank, characterized in that: Also included is a controller, the controller comprising: An acquisition module is used to obtain historical liquid level data of the regulating tank; A scheduling module is used to generate a one-day water inflow plan for the biochemical pool according to the historical liquid level data of the regulating pool; the water inflow plan includes a plurality of water inflow periods and stop periods that alternate in turn; the scheduling module is used to divide the continuous period in which the liquid level in the historical liquid level data of the regulating pool is continuously above 65% of the regulating pool volume and maintained for more than 1 hour as the peak period in the water inflow plan; a zero week is inserted into the period immediately adjacent to the peak period or the period staggered from the peak period, and the remaining period is the stop period, so that the duration of a single water inflow period containing the zero week is less than the maximum continuous water inflow duration, and the duration of a single stop period is less than the maximum static duration; The execution module is used to control the lifting pump of the regulating tank to feed water into the biochemical tank during the water inlet period, and after delaying the preset flow time from the starting point of the water inlet period, control the dosing pump to add medicine to the last section of the aerobic tank according to the preset dosing amount, and control the blower to aerate the aerobic tank according to the theoretical aeration time.

Images