Rain sewage treatment system for sponge city

Abstract

The invention relates to the technical field of sewage treatment, in particular to a rainwater and sewage treatment system for a sponge city. The system comprises a rainwater treatment data acquisition module for acquiring water flow data of a reservoir and the content of each pollutant in water before and after purification; the rainwater treatment data analysis module is used for acquiring the content state coefficient of each pollutant and the influence coefficient of each pollutant in each time period; the decontamination influence coefficient of each time period is obtained, and the decontamination power index of each time period is determined by combining the content difference of pollutants before and after purification in each time period; and the rain and sewage treatment module is used for acquiring the duty ratio of a PWM regulator in the next time period based on the dirt-removing power index of each time period, and regulating the ultraviolet irradiation intensity in the water purification process in the next time period. The rainwater sewage treatment efficiency of the sponge city is improved.

Description

Technical Field

[0001] The present application relates to the technical field of sewage treatment, and in particular to a rainwater and sewage treatment system for sponge cities. Background Art

[0002] The core concept of sponge city is to make the city like a sponge, with excellent flexibility in adapting to environmental changes and responding to natural disasters caused by rainwater. Specifically, sponge city uses a variety of technical means such as "infiltration, retention, storage, purification, use and discharge" to achieve the purpose of natural accumulation, infiltration and purification of rainwater.

[0003] In the urban rainwater and sewage treatment system, the infiltration, retention and storage functions are designed to collect rainwater and store it in a water storage module group. Since the collected rainwater and sewage contain a large amount of organic pollutants, silt particles and other substances, if used directly, it may cause varying degrees of adverse effects on the environment. The collected rainwater is purified to reduce the degree of pollution. In the purification process, solid pollutants are first filtered out using a filter tank, and then an ultraviolet disinfection device is used for disinfection. At the same time, the water in the reservoir is stirred with an aeration disk to improve the water quality. However, the current rainwater and sewage treatment system fails to fully consider the impact of changes in water storage rate and rainwater pollution level, making it difficult for conventional water purification methods to stably remove pollutants, resulting in a low water purification efficiency of the treatment system. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of this application is to provide a rainwater and sewage treatment system for sponge cities. The technical solutions adopted are as follows: The present application proposes a rainwater and sewage treatment system for a sponge city, the system comprising: The rainwater treatment data collection module obtains the water flow data of the reservoir, as well as the content of each pollutant in the water before and after purification; The rainwater treatment data analysis module analyzes the correlation between the water flow data and the content of each pollutant in each time period, and obtains the state coefficient of each pollutant content in each time period based on the data change degree of each pollutant content in each time period; Based on the proportion of the state coefficient of each pollutant content in each time period and the average level of each pollutant content in each time period, the impact coefficient of each pollutant in each time period is obtained; The pollution degree value of each time period is obtained by combining the influence coefficients of all pollutants, and the decontamination influence coefficient of each time period is determined according to the difference between the pollution degree values ​​of each time period and its adjacent time periods; Based on the decontamination influence coefficient of each time period and the difference in pollutant content before and after purification in each time period, the decontamination capacity index of each time period is determined; The rainwater and sewage treatment module obtains the duty cycle of the PWM regulator in the next time period based on the decontamination capacity index of each time period and the preset duty cycle of the PWM regulator, and adjusts the ultraviolet irradiation intensity in the water purification process in the next time period.

[0005] Preferably, the pollutant content includes sludge content and COD content.

[0006] Preferably, obtaining the state coefficient of each pollutant content in each time period includes: ; In the formula, represents the state coefficient of the w-th pollutant content in the i-th time period, represents the water flow data in the i-th time period, represents the content data of the wth pollutant in the i-th time period, represents the Spearman correlation coefficient, represents an exponential function with a natural constant as base, is the content variation coefficient of the w-th pollutant in the ith time period, which is obtained by the content data change of the w-th pollutant in the ith time period.

[0007] Preferably, the acquisition of the content variation coefficient further includes: the cumulative sum of the first-order difference sequence corresponding to the w-th pollutant content data in the i-th time period as the content variation coefficient of the w-th pollutant in the i-th time period.

[0008] Preferably, obtaining the influence coefficient of each pollutant in each time period includes: The ratio of each pollutant content state coefficient to the sum of all pollutant content state coefficients is calculated, and the product of the ratio and the average content of each pollutant in each time period is used as the influence coefficient of each pollutant in each time period.

[0009] Preferably, the pollution degree value of each time period is the sum of the impact coefficients of all pollutants in each time period.

[0010] Preferably, a plurality of time periods before each time period are used as adjacent time periods of each time period.

[0011] Preferably, the determination of the decontamination influence coefficient of each time period includes: ; In the formula, represents the decontamination influence coefficient of the i-th time period, represents the number of neighboring time periods of the i-th time period, represents an exponential function with a natural constant as base, , Represent the pollution degree values ​​in the i-th and b-th time periods respectively.

[0012] Preferably, the determination of the decontamination capacity index of each time period includes: ; In the formula, represents the decontamination capacity index of the i-th time period, represents the decontamination influence coefficient of the i-th time period, It represents the difference between the mean content of the w-th pollutant before purification and the mean content of the w-th pollutant after purification in the i-th time period, and W is the number of pollutant types.

[0013] Preferably, the step of obtaining the duty cycle of the PWM regulator in the next time period further includes: , where is the duty cycle of the PWM regulator in the i+1th time period, To preset the duty cycle of the PWM regulator, It represents the normalized result of the decontamination ability index in the i-th time period.

[0014] This application has the following beneficial effects: This application optimizes and adjusts the problem of low water purification efficiency in the purification treatment link of the sponge city rainwater and sewage treatment system. By deeply exploring the correlation between the content of various pollutants in sewage and the water storage efficiency, as well as the changing characteristics of each pollutant itself, the corresponding state coefficients of each pollutant content are obtained. According to the proportion of the state coefficients of each pollutant content and the actual value of the pollutant content, the pollution degree value is accurately calculated. Compared with the judgment based on the data directly collected by the sensor, the pollution degree value can more accurately present the actual pollution status of the currently collected rainwater and sewage; Further analysis of the changes in pollution levels, combined with the characteristics of pollution level changes and the synchronization characteristics of the decontamination state, calculated the decontamination efficiency value to reflect the rainwater and sewage purification efficiency in the treatment system. Based on the obtained decontamination efficiency value, the light intensity of the ultraviolet lamp is adjusted, thereby effectively improving the water purification efficiency of the treatment system, providing a strong guarantee and optimization strategy support for the efficient and stable operation of the sponge city rainwater and sewage treatment system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0016] Figure 1A block diagram of a rainwater and sewage treatment system for a sponge city provided in one embodiment of the present application; Figure 2 A schematic diagram of the sponge city rainwater and sewage treatment process provided for one embodiment of the present application. DETAILED DESCRIPTION

[0017] In order to further explain the technical means and effects adopted by this application to achieve the predetermined invention purpose, the following is a detailed description of the specific implementation method, structure, characteristics and effects of a rainwater and sewage treatment system for a sponge city proposed in this application in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0018] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0019] The specific scheme of a rainwater and sewage treatment system for a sponge city provided by the present application is described in detail below with reference to the accompanying drawings.

[0020] See also Figure 1 , which shows a block diagram of a rainwater and sewage treatment system for a sponge city provided by an embodiment of the present application. The system includes: a rainwater treatment data collection module, a rainwater treatment data analysis module, and a rainwater and sewage treatment module.

[0021] The rainwater treatment data collection module obtains the water flow data of the reservoir and the content of each pollutant in the water before and after purification.

[0022] In this embodiment, a PP water storage module group is used to collect rainwater during the rainwater and sewage treatment process, and the collected rainwater is decontaminated by a water purification module. The water purification module contains a filter tank, an aeration device is installed at the bottom of the water purification tank, and an ultraviolet disinfector is installed on the top of the water inlet tank. The purified water is transported to the clean water tank for use at any time.

[0023] In order to analyze the influence of changes in water storage efficiency and rainwater pollution degree, this embodiment uses a flow detection instrument to obtain water flow data of the water storage tank. Further, the content of pollutants in the water before and after purification is collected. In this embodiment, the silt content data in the water before and after rainwater purification is collected by a silt density index measuring instrument, and the COD (chemical oxygen demand) data in the water before and after rainwater purification is collected by a COD detector. The COD content reflects the degree of organic matter pollution in the water body. In this embodiment, the time interval for collecting the above data is set to 3 minutes.

[0024] At this point, the water flow data at each time is obtained, as well as the content of each pollutant in the water before and after purification, including the sludge content and COD content in this embodiment.

[0025] The rainwater treatment data analysis module analyzes the correlation between the water flow data and the content of each pollutant in each time period, and obtains the state coefficient of each pollutant content in each time period in combination with the data change degree of each pollutant content in each time period; obtains the impact coefficient of each pollutant in each time period based on the proportion of the state coefficient of each pollutant content in each time period and the average level of each pollutant content in each time period; obtains the pollution degree value of each time period in combination with all pollutant impact coefficients, and determines the pollution removal impact coefficient of each time period according to the difference in pollution degree values ​​between each time period and its adjacent time periods; determines the pollution removal capacity index of each time period based on the pollution removal impact coefficient of each time period and the difference in pollutant content before and after purification in each time period.

[0026] The rainwater and sewage treatment system of sponge city realizes the collection, infiltration, purification and utilization of rainwater by constructing diversified facilities such as green roofs, permeable pavement, rainwater gardens, sunken green spaces, rainwater wetlands and reservoirs. At the same time, the excess rainwater is orderly guided to the urban drainage system through the rainwater pipe network system to reduce the risk of urban waterlogging and improve the utilization rate of water resources. Among them, some projects such as green roofs and permeable pavement can reduce runoff from the source and purify the initial rain pollution. However, rainwater collected from other channels encounters more runoff, and these rainwaters with more runoff contain more pollutants. In addition, the amount of rainwater collected from different channels is unstable, which makes the degree of pollution of rainwater and sewage in the water storage module group vary greatly. The collected rainwater and sewage will first pass through the filter tank to filter the solids with larger particle size. The filtered rainwater and sewage contain silt and organic pollutants with smaller particle size, and then they are decontaminated by aeration and ultraviolet disinfection in the water purification tank to obtain clean rainwater. In the process of ultraviolet sterilization and decontamination, the pollution degree of rainwater and sewage is constantly changing. It is difficult to balance the balance of achieving good decontamination and reducing the waste of ultraviolet lamp resources by sterilizing only according to the preset ultraviolet irradiation parameters. Therefore, the changing characteristics of water storage rate and rainwater pollution degree are comprehensively considered to achieve more efficient rainwater and sewage purification.

[0027] As the water storage rate increases, the requirements for sewage purification efficiency also increase, and accordingly, the irradiation intensity of the ultraviolet lamp also needs to be increased accordingly. Therefore, the accumulation rate of rainwater has a certain influence on the sewage purification effect. In addition, factors such as dissolved organic and inorganic substances in water and undissolved suspended solids will affect the transmittance of ultraviolet rays, while sludge particles can absorb and reflect ultraviolet rays, preventing them from irradiating the DNA of bacteria and viruses, thereby affecting sterilization. Therefore, the degree of pollution of rainwater and sewage will also affect the purification effect. In addition, the content of organic pollutants and silt particles in the collected rainwater and sewage may continue to increase with the continuation of rainfall. This is because in a continuous rainfall environment, the stronger the ability of rainwater to wash the surface, the more silt materials and other pollutants may be washed into the water storage module group, which makes the water flow data show a certain positive correlation with the silt content data and COD content data of rainwater before purification. From the above analysis, it can be seen that the stronger the positive correlation between the water flow data and the content of pollutants in sewage, and the more significant the increase in the content of pollutants, the stronger the purification capacity is needed.

[0028] Based on the duration of rainfall in general cities and the rapid changes in the degree of rainwater pollution, this embodiment uses a time length of 1 hour as a time period. Further analysis is made of the changing relationship between the water flow in the water storage module group and the silt content data and COD content data of the rainwater before purification. For the w-th pollutant in the i-th time period, in order to obtain the changing characteristics of the pollutant content, this embodiment calculates the first-order difference sequence of the silt content data in the time period, and the cumulative sum of all data in the first-order difference sequence obtained is recorded as the content change coefficient of the w-th pollutant in the i-th time period. , which is used to reflect the increase and decrease trend of sludge pollutants in this time period. Since the measured pollutant content data may have a certain deviation from the actual pollutant content in rainwater and sewage, the wth pollutant content state coefficient is calculated in combination with the relevant characteristics of the water flow. In this embodiment, the calculation formula is: ; In the formula, represents the state coefficient of the w-th pollutant content in the i-th time period, represents the water flow data in the i-th time period, represents the content data of the wth pollutant in the i-th time period, represents the Spearman correlation coefficient, represents an exponential function with a natural constant as base, is the coefficient of change of the content of the w-th pollutant in the ith time period, which is obtained by the change in the content data of the w-th pollutant in the ith time period. In this embodiment, the cumulative sum of the first-order difference sequences corresponding to the content data of the w-th pollutant in the ith time period is used as the coefficient of change of the content of the w-th pollutant in the ith time period.

[0029] Income The larger the value, the stronger the positive correlation between silt content and water storage rate. The value range of the Spearman correlation coefficient is [-1,1]. Adding 1 to the formula can avoid the result being negative. The larger the value, the more obvious the increase in the content of the wth pollutant. The larger it is, the more obvious the potential increase in the content of the wth pollutant in the collected rainwater and sewage is.

[0030] So far, through the above process in this embodiment, the sludge content state coefficient and the COD content state coefficient in the i-th time period are obtained.

[0031] Organic matter and sludge particles in the water will affect the decontamination effect of ultraviolet rays. However, the degree of influence of organic matter and particles on ultraviolet decontamination may be inconsistent. In order to comprehensively consider the impact of different pollutants on subsequent purification efficiency, the influence coefficients of each pollutant in each time period are obtained based on the proportion of the state coefficients of each pollutant content in each time period and the average level of each pollutant content in each time period. Specifically, the ratio of the state coefficient of each pollutant content to the sum of the state coefficients of all pollutant contents is calculated, and the product of the ratio and the average value of each pollutant content in each time period is used as the influence coefficient of each pollutant in each time period. For ease of understanding, in this embodiment, the calculation formula for the influence coefficient of each pollutant is: ; In the formula, represents the impact coefficient of the w-th pollutant in the i-th time period, represents the mean value of the w-th pollutant content data in the i-th time period, W is the number of pollutant types. In this embodiment, there are two types of pollutants, sludge and COD, that is, W=2, and the obtained The larger it is, the greater the impact of the w-th pollutant content on the pollution degree.

[0032] Further, according to the influence coefficients of all pollutants in each time period, the pollution degree value of each time period is obtained, and the sum of all pollutant influence coefficients is used as the pollution degree value of each time period. In this embodiment, the sum of the sludge influence coefficient and the COD influence coefficient is used as the pollution degree value of the i-th time period, which is recorded as . The larger it is, the greater the degree of pollution in the rainwater in the i-th time period.

[0033] In this embodiment, the rainwater and sewage purification process is regulated and controlled based on the changes in the pollution level of rainwater and sewage. Due to the various ways of collecting rainwater and sewage, the changes in the pollution level of rainwater are unstable, which makes it difficult to achieve precise regulation of the sterilization efficiency. The impact of the pollution level on the ultraviolet decontamination efficiency can be further analyzed based on the changing characteristics of the pollution state. The first N time periods of each time period are set as the neighboring time periods of each time period. In this embodiment, N is 6. According to the difference in the pollution level values ​​of each time period and the neighboring time periods, the decontamination impact coefficient of each time period is calculated as follows: ; In the formula, represents the decontamination influence coefficient of the i-th time period, represents the number of neighboring time periods of the i-th time period, represents an exponential function with a natural constant as base, , Respectively represent the pollution degree values ​​of the i-th and b-th time periods. It can be understood that The larger the value, the more serious the pollution status of the i-th time period is compared with its neighboring time period b-th time period. The larger it is, the more unstable the pollution level in the corresponding adjacent time period is, and the greater the impact on the decontamination efficiency is.

[0034] In the water treatment process, it is necessary to regulate the subsequent purification process in real time according to the dynamic changes in the degree of pollution and the effectiveness of the decontamination in the current specific time period. Among them, the decontamination status of the current time period can be expressed according to the difference in the content of pollutants in the water before and after purification. Specifically, when the decontamination influence coefficient of a certain time period presents a large value, it means that the total amount of pollutants contained in the rainwater and sewage is on the rise. In this case, if the change range of the pollutant content of rainwater before and after the purification operation in this time period is small, that is, the difference between the two is small, it indicates that the pollutants have not been removed in a timely and effective manner. Therefore, by deeply analyzing the changing characteristics of the decontamination state in different time periods reflected by the decontamination influence coefficient, and combining the synchronous correlation between the pollutant content of rainwater before and after purification, it can provide a key basis for the precise regulation of the water treatment process. For example, if the decontamination influence coefficient continues to increase for multiple consecutive time periods, and the difference in pollutant content before and after purification is always maintained at a low level, it is necessary to optimize and adjust the purification process parameters to improve the decontamination efficiency and ensure that the water quality meets the standards. Then, based on the decontamination influence coefficient of each time period and the difference in the content of pollutants before and after purification in each time period, the decontamination capacity index is calculated. The specific calculation formula is: ; In the formula, represents the decontamination capacity index of the i-th time period, represents the decontamination influence coefficient of the i-th time period, It represents the difference between the mean content of the w-th pollutant before purification and the mean content of the w-th pollutant after purification in the i-th time period, and W is the number of pollutant types.

[0035] It is understandable that the The smaller the value, the less pollutants in the rainwater were removed in time. The smaller it is, the worse the decontamination efficiency is during this period of time.

[0036] The rainwater and sewage treatment module obtains the duty cycle of the PWM regulator in the next time period based on the decontamination capacity index of each time period and the preset duty cycle of the PWM regulator, and adjusts the ultraviolet irradiation intensity in the water purification process in the next time period.

[0037] This embodiment calculates the state coefficients of sludge and COD content by obtaining the correlation characteristics between the sludge and organic matter content and the water storage rate in rainwater, and the change characteristics of the pollutant content. The pollution degree value is calculated by combining the average value of each pollutant content in the time period, and the change characteristics of the pollution degree and the synchronization characteristics of the decontamination state are further analyzed to calculate the decontamination capacity index. This value reflects the decontamination efficiency of the water purification device in the current time period. The smaller the obtained decontamination capacity index, it indicates that the pollutants in the collected rainwater may not be effectively removed. At this time, a larger ultraviolet irradiation intensity needs to be set to improve the decontamination efficiency; the larger the obtained decontamination capacity index, it indicates that the pollutants in the collected rainwater are in a good state of removal. At this time, a smaller ultraviolet irradiation intensity can be set to avoid waste of resources and extend the service life of the lamp.

[0038] This embodiment adjusts the light intensity of the ultraviolet lamp by controlling the duty cycle of the PWM regulator, thereby controlling the decontamination ability of rainwater. Specifically, the duty cycle adjustment formula is: ,in is the duty cycle of the PWM regulator in the i+1th time period, is the preset duty cycle of the PWM regulator, which ranges from 0 to 1 and is set to 0.2 in this embodiment. The normalized result of the decontamination capacity index in the i-th time period is represented. There are many normalization methods. This embodiment uses the tanh function to achieve normalization. According to the duty cycle of the PWM regulator in the i+1-th time period, the rainwater and sewage are decontaminated in the water purification tank. This helps to improve the water purification efficiency while avoiding resource waste.

[0039] Specifically, in this embodiment, the schematic diagram of the sponge city rainwater and sewage treatment process is as follows: Figure 2 shown.

[0040] It should be noted that the sequence of the above embodiments of the present application is only for description and does not represent the advantages and disadvantages of the embodiments. The processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0041] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0042] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present application should be included in the protection scope of the present application.

Claims

1. A rainwater and sewage treatment system for a sponge city, characterized in that: The system comprises: The rainwater treatment data collection module obtains the water flow data of the reservoir, as well as the content of each pollutant in the water before and after purification; The rainwater treatment data analysis module analyzes the correlation between the water flow data and the content of each pollutant in each time period, and obtains the state coefficient of each pollutant content in each time period based on the data change degree of each pollutant content in each time period; Based on the proportion of the state coefficient of each pollutant content in each time period and the average level of each pollutant content in each time period, the impact coefficient of each pollutant in each time period is obtained; The pollution degree value of each time period is obtained by combining the influence coefficients of all pollutants, and the decontamination influence coefficient of each time period is determined according to the difference between the pollution degree values ​​of each time period and its adjacent time periods; Based on the decontamination influence coefficient of each time period and the difference in pollutant content before and after purification in each time period, the decontamination capacity index of each time period is determined; The rainwater and sewage treatment module obtains the duty cycle of the PWM regulator in the next time period based on the decontamination capacity index of each time period and the preset duty cycle of the PWM regulator, and adjusts the ultraviolet irradiation intensity in the water purification process in the next time period.

2. A rainwater and sewage treatment system for a sponge city as claimed in claim 1, characterized in that: The pollutant content includes sludge content and COD content.

3. A rainwater and sewage treatment system for a sponge city as claimed in claim 1, characterized in that: The acquisition of the state coefficient of each pollutant content in each time period includes: ; In the formula, represents the state coefficient of the w-th pollutant content in the i-th time period, represents the water flow data in the i-th time period, represents the content data of the wth pollutant in the i-th time period, represents the Spearman correlation coefficient, represents an exponential function with a natural constant as base, is the content variation coefficient of the w-th pollutant in the ith time period, which is obtained by the content data change of the w-th pollutant in the ith time period.

4. A rainwater and sewage treatment system for a sponge city as claimed in claim 3, characterized in that: The acquisition of the content variation coefficient further includes: the cumulative sum of the first-order difference sequence corresponding to the w-th pollutant content data in the i-th time period is used as the content variation coefficient of the w-th pollutant in the i-th time period.

5. A rainwater and sewage treatment system for a sponge city as claimed in claim 1, characterized in that: The acquisition of the impact coefficient of each pollutant in each time period includes: The ratio of each pollutant content state coefficient to the sum of all pollutant content state coefficients is calculated, and the product of the ratio and the average content of each pollutant in each time period is used as the influence coefficient of each pollutant in each time period.

6. A rainwater and sewage treatment system for a sponge city as claimed in claim 1, characterized in that: The pollution degree value of each time period is the sum of the impact coefficients of all pollutants in each time period.

7. A rainwater and sewage treatment system for a sponge city as claimed in claim 1, characterized in that: The multiple time periods before each time period are regarded as the neighboring time periods of each time period.

8. A rainwater and sewage treatment system for a sponge city as claimed in claim 1, characterized in that: The determination of the decontamination influence coefficient of each time period includes: ; In the formula, represents the decontamination influence coefficient of the i-th time period, represents the number of neighboring time periods of the i-th time period, represents an exponential function with a natural constant as base, , Represent the pollution degree values ​​in the i-th and b-th time periods respectively.

9. A rainwater and sewage treatment system for a sponge city as claimed in claim 1, characterized in that: The determination of the decontamination capacity index of each time period includes: ; In the formula, represents the decontamination capacity index of the i-th time period, represents the decontamination influence coefficient of the i-th time period, It represents the difference between the mean content of the w-th pollutant before purification and the mean content of the w-th pollutant after purification in the i-th time period, and W is the number of pollutant types.

10. A rainwater and sewage treatment system for a sponge city as claimed in claim 1, characterized in that: The step of obtaining the duty cycle of the PWM regulator in the next time period further includes: , where is the duty cycle of the PWM regulator in the i+1th time period, To preset the duty cycle of the PWM regulator, It represents the normalized result of the decontamination ability index in the i-th time period.

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