Prediction method of time consumption for aerobic stabilization remediation of landfill based on piecewise nonlinear function

Abstract

The present invention discloses a method for predicting the time consumption of aerobic stabilization and restoration of landfills based on piecewise nonlinear functions. The method takes the garbage of the landfill to be predicted as the main body, carries out a small-scale simulation experiment under the design parameters of the aerobic stabilization project of the landfill, obtains a curve of the change of pollutant concentration with aeration time; establishes a piecewise nonlinear function model; substitutes the experimental data obtained from the small-scale simulation experiment into the piecewise nonlinear function model, respectively determines the model parameters of each type of pollutant with the highest fitting coefficient, and obtains a model set composed of piecewise nonlinear function models for the degradation of each type of pollutant; based on the piecewise nonlinear function models corresponding to each pollutant, obtains the time required for its concentration to drop to the threshold value of the aerobic stabilization endpoint. The method for predicting the time consumption of aerobic stabilization and restoration of landfills based on piecewise nonlinear functions of the present invention can realize the prediction of the endpoint of aerobic stabilization processes in different landfills.

Description

Technical Field

[0001] The invention belongs to the technical field of landfill restoration, and specifically is a landfill aerobic stabilization restoration time-consuming prediction method based on piecewise nonlinear functions. Background Art

[0002] Landfill is the main method of harmless treatment of domestic waste in my country, and it absorbs nearly 70% of domestic waste. At present, landfills are spread all over the country. Without artificial regulation, traditional landfills generally take 30-50 years to be completely stable after closure. During the long degradation cycle, landfills will continue to produce pollutants such as leachate and landfill gas, which require long-term post-maintenance to eliminate their impact on the surrounding environment. The post-maintenance cost is high, and the landfills occupy land for a long time. Under the current rapid urbanization process, the contradiction between the supply and demand of land resources has been aggravated. In view of this, it is urgent to carry out landfill management and achieve its rapid stabilization and reclamation.

[0003] Among the many landfill management methods, aerobic stabilization has attracted wide attention from all walks of life due to its advantages such as low cost, low leachate production, low greenhouse gas emissions, and short management cycle. For example, Chinese patent publication number CN111495918B discloses a landfill cluster well gas injection control method, and Chinese patent publication number CN113578912A discloses a landfill aerobic microbial stabilization system and method. These studies intend to shorten the aerobic stabilization process through technical improvements such as optimizing process parameters and adding functional microorganisms, which has promoted the application of technology.

[0004] In addition, the establishment of a garbage degradation model in the process of aerobic stabilization is conducive to predicting the time required to reach the end of the restoration, which is of great significance to government planning decisions, project management, construction schedule, etc. "Aerobic Restoration Experiment and Numerical Simulation of Old Garbage Landfill" (Master's thesis of Huazhong University of Science and Technology, Zhang Junlong) describes the change of pollutant concentration based on an exponential function model, but the model only focuses on the pollutant concentration decrease stage dominated by the intracellular metabolism of dissolved organic matter after subsequent hydrolysis, and does not consider the pollutant concentration increase stage dominated by the extracellular hydrolysis of solid matter into dissolved organic matter in the early stage. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a method for predicting the time consumption of aerobic stabilization and remediation of landfills based on piecewise nonlinear functions, which can realize the prediction of the end point of aerobic stabilization process of different landfills.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for predicting the time consumption of aerobic stabilization remediation of landfills based on piecewise nonlinear functions is proposed. The waste in the landfill to be predicted is used as the main body. A small-scale simulation experiment is carried out under the design parameters of the aerobic stabilization project of the landfill to obtain the curve of the change of pollutant concentration with aeration time.

[0008] Establish a piecewise nonlinear function model:

[0009]

[0010] Where y represents pollutant concentration; x represents time variable; x1 represents the time variable dividing point corresponding to the maximum peak value of pollutant concentration; b represents the aeration time corresponding to the maximum peak value of pollutant concentration; a and k are both model parameters; c represents the end point of the pollutant concentration increase phase x∈[0,x1); C represents the starting point of the pollutant concentration decrease phase x∈[x1,+∞);

[0011] Substitute the experimental data obtained from the small-scale simulation experiment into the piecewise nonlinear function model, determine the model parameters a and k of each type of pollutant with the highest fitting coefficient, and obtain a model set consisting of piecewise nonlinear function models for the degradation of various types of pollutants;

[0012] Based on the piecewise nonlinear function model corresponding to each pollutant, the time required for its concentration to drop to the aerobic stabilization endpoint threshold is obtained.

[0013] Furthermore, after substituting the experimental data obtained from the small-scale simulation experiment into the piecewise nonlinear function model, the model parameters a and k of each type of pollutant with the highest fitting coefficient were determined by the least squares method.

[0014] Furthermore, the aerobic stabilization endpoints of each pollutant in the garbage are:

[0015] The aerobic stabilization endpoint threshold of (cellulose + hemicellulose) / lignin ((C+H) / L) is 0.2;

[0016] The aerobic stabilization endpoint threshold of biodegradability (BDM) is 3%;

[0017] The aerobic stabilization endpoint threshold of the chemical oxygen demand (COD) of the leachate is 100 mg / L;

[0018] The aerobic stabilization endpoint threshold of ammonia nitrogen is 25 mg / L.

[0019] Furthermore, based on the piecewise nonlinear function model corresponding to each pollutant and the initial concentration C0 of the pollutant at the beginning of aeration, the time T1 required for the pollutant concentration to rise from the initial concentration C0 and then drop to the initial concentration C'0 is estimated; then the time T2 required for the pollutant to continuously drop from the concentration C'0 to the aerobic stabilization endpoint is estimated, and the time T required for the aerobic stabilization endpoint is obtained as:

[0020] T=T1+T2.

[0021] The beneficial effects of the present invention are:

[0022] The present invention is based on a piecewise nonlinear function-based landfill aerobic stabilization and remediation time prediction method. Combined with the characteristics that the pollutant concentration first increases and then decreases during the aerobic stabilization process of the landfill, a piecewise nonlinear function model is created. The model parameters a and k of various pollutants with the highest fitting coefficients are determined respectively using experimental data obtained from small-scale simulation experiments. The time required for the concentration of each pollutant to drop to the aerobic stabilization endpoint threshold can be obtained, thereby realizing the prediction of the landfill aerobic stabilization and remediation time, which is helpful for project implementation management. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to make the purpose, technical solution and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration:

[0024] Figure 1 It is a flow chart of an embodiment of a method for predicting time consumption of aerobic stabilization and restoration of landfill based on piecewise nonlinear function of the present invention;

[0025] Figure 2 The following are the curves showing the changes of the concentration of each pollutant in the garbage with the aeration time; (a) is the curve showing the changes of the concentration of (C+H) / L with the aeration time; (b) is the curve showing the changes of the concentration of BDM with the aeration time; (c) is the curve showing the changes of the concentration of COD with the aeration time; (d) is the curve showing the changes of the concentration of ammonia nitrogen with the aeration time;

[0026] Figure 3 = (C+H) / L from the initial concentration C0 to the aerobic stabilization endpoint threshold C end Schematic diagram of the time required. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0028] The present embodiment provides a method for predicting the time consumption of aerobic stabilization and restoration of a landfill based on a piecewise nonlinear function, and includes the following contents.

[0029] Taking the landfill waste to be predicted as the main body, a small-scale simulation experiment was carried out under the design parameters of the aerobic stabilization project of the landfill to obtain the curve of pollutant concentration changing with aeration time.

[0030] Specifically, this embodiment collects an appropriate amount of garbage at the landfill to be predicted. The design parameters of the aerobic stabilization project of the landfill are: the aeration mode is continuous low pressure, the aeration flow rate is 450L / h, and the water content of the reinjected leachate is guaranteed to be 50%-60%. A small-scale simulation experiment was carried out under the design conditions. Garbage was collected every 3 days in the temperature rise section and high temperature section greater than or equal to 40°C, and the temperature was adjusted to once every 5 days when it was lowered to below 40°C. When the leachate output is large in the early stage, the leachate is collected every 2 days. When the leachate output is small in the later stage, the leachate is collected every 5 days. The pollutants monitored in the garbage are cellulose (C), hemicellulose (H), lignin (L) and BDM, and the pollutants monitored in the leachate are COD and ammonia nitrogen. The changes in (C+H) / L, BDM, and COD and ammonia nitrogen of the leachate with aeration time are plotted, as shown Figure 2 shown.

[0031] Establish a piecewise nonlinear function model:

[0032]

[0033] Among them, y represents the pollutant concentration; x represents the time variable; x1 represents the time variable dividing point corresponding to the maximum peak value of the pollutant concentration; b represents the aeration time corresponding to the maximum peak value of the pollutant concentration; a and k are both model parameters; c represents the end point of the pollutant concentration increasing stage x∈[0,x1); C represents the starting point of the pollutant concentration decreasing stage x∈[x1,+∞).

[0034] Substitute the experimental data obtained from the small-scale simulation experiment into the piecewise nonlinear function model, determine the model parameters a and k of each type of pollutant with the highest fitting coefficient, and obtain a model set composed of piecewise nonlinear function models for the degradation of each type of pollutant. Specifically, in this embodiment, after substituting the experimental data obtained from the small-scale simulation experiment into the piecewise nonlinear function model, different functions are used to perform nonlinear fitting on the two segments of data, and the model parameters a and k of each type of pollutant with the highest fitting coefficient are determined by the least squares method.

[0035] The measured values ​​of pollutants in the aerobic stabilization degradation process are fitted into the piecewise nonlinear function model, and the horizontal coordinate corresponding to the maximum peak value of the pollutant concentration is determined as the time variable demarcation point x1. Taking (C+H) / L as an example, Figure 2(a) It can be seen that the scattered points are measured values ​​and the curves are simulated values. Since the concentration of (C+H) / L reaches a peak value (5.34) on the 9th day, we can first determine b=9, c=5.34, and C=5.34. By using the least squares method, we can determine that when the fitting degree is the highest (0.9325), a=-0.018 and k=0.025, then:

[0036] The piecewise nonlinear function model of (C+H) / L is:

[0037]

[0038] Similarly, the piecewise nonlinear function model of BDM is:

[0039]

[0040] The piecewise nonlinear function model of ammonia nitrogen is:

[0041]

[0042] The piecewise nonlinear function model of COD is:

[0043]

[0044] Based on the piecewise nonlinear function model corresponding to each pollutant, the time required for its concentration to drop to the aerobic stabilization endpoint threshold is obtained. Specifically, in this embodiment, based on the piecewise nonlinear function model corresponding to each pollutant, combined with the initial concentration C0 of the pollutant when aeration begins, the time T1 required for the pollutant concentration to rise from the initial concentration C0 and then drop to the initial concentration C'0 is first estimated; then the time T2 required for the pollutant to continuously drop from the concentration C'0 to the aerobic stabilization endpoint threshold is estimated, and the time T required for the aerobic stabilization endpoint is obtained as:

[0045] T=T1+T2.

[0046] Specifically, in this embodiment, the aerobic stabilization endpoint of each pollutant in the garbage is:

[0047] The aerobic stabilization endpoint threshold of (cellulose + hemicellulose) / lignin ((C+H) / L) is 0.2;

[0048] The aerobic stabilization endpoint threshold of biodegradability (BDM) is 3%;

[0049] The aerobic stabilization endpoint threshold of the chemical oxygen demand (COD) of the leachate is 100 mg / L;

[0050] The aerobic stabilization endpoint threshold of ammonia nitrogen is 25 mg / L.

[0051] According to sampling and analysis, the initial concentration of (C+H) / L in the landfill garbage was 3.62, the initial concentration of BDM was 0.20%, the initial concentration of ammonia nitrogen in the leachate was 9952.47 mg / L, and the initial concentration of COD was 732.51 mg / L.

[0052] like Figure 3 As shown, taking (C+H) / L as an example, it is known that the initial concentration of (C+H) / L is C0=3.62, and the maximum peak value of (C+H) / L is C max =5.34, the corresponding horizontal coordinate x=9; thus, the time variable demarcation point of the piecewise nonlinear function model of (C+H) / L is x1=9, and the concentration of (C+H) / L increases from the initial concentration C0 to the maximum peak value C max The time required is t1, from the maximum peak C max The time required to reach C'0 is t2, that is:

[0053]

[0054] t1+t2=T1

[0055] Combining the known conditions, we can get T1 = 24.5 days.

[0056] It is known that the aerobic stabilization endpoint threshold of (C+H) / L is C end = 0.2, then the concentration of (C+H) / L increases from C'0 to C end The required time is T2 which can be expressed as:

[0057]

[0058] So T2 = 115.8 days.

[0059] (C+H) / L from the initial concentration C0 to the aerobic stabilization end point C end The time required is T=T1+T2, so T=140.3 days.

[0060] Similarly, the time required for BDM, COD and ammonia nitrogen to reach the aerobic stabilization endpoint threshold can be obtained, see Table 1.

[0061] Table 1 Prediction of the time required to reach the stabilization endpoint of a landfill

[0062]

[0063] The above-described embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or changes made by those skilled in the art based on the present invention are within the protection scope of the present invention. The protection scope of the present invention shall be subject to the claims.

Claims

1. A method for predicting the time consumption of aerobic stabilization and restoration of landfills based on piecewise nonlinear functions, characterized in that: Taking the landfill waste to be predicted as the main body, a small-scale simulation experiment was carried out under the design parameters of the aerobic stabilization project of the landfill to obtain the curve of pollutant concentration changing with aeration time; Establish a piecewise nonlinear function model: Where y represents pollutant concentration; x represents time variable; x1 represents the time variable dividing point corresponding to the maximum peak value of pollutant concentration; b represents the aeration time corresponding to the maximum peak value of pollutant concentration; a and k are both model parameters; c represents the end point of the pollutant concentration increase phase x∈[0,x1); C represents the starting point of the pollutant concentration decrease phase x∈[x1,+∞); Substitute the experimental data obtained from the small-scale simulation experiment into the piecewise nonlinear function model, determine the model parameters a and k of each type of pollutant with the highest fitting coefficient, and obtain a model set consisting of piecewise nonlinear function models for the degradation of various types of pollutants; Based on the piecewise nonlinear function model corresponding to each pollutant, the time required for its concentration to drop to the aerobic stabilization endpoint threshold is obtained; Based on the piecewise nonlinear function model corresponding to each pollutant, combined with the initial concentration C0 of the pollutant when aeration begins, the time T1 required for the pollutant concentration to rise from the initial concentration C0 and then drop to the initial concentration C'0 is estimated; then the time T2 required for the pollutant to continuously drop from the concentration C'0 to the aerobic stabilization endpoint is estimated, and the time T required for the aerobic stabilization endpoint is obtained as: T=T1+T2.

2. The time-consuming prediction method for aerobic stabilization and restoration of landfill based on piecewise nonlinear function according to claim 1 is characterized by: After substituting the experimental data obtained from the small-scale simulation experiment into the piecewise nonlinear function model, the model parameters a and k of each type of pollutant with the highest fitting coefficient were determined by the least squares method.

3. The time-consuming prediction method for aerobic stabilization and restoration of landfill based on piecewise nonlinear function according to claim 1 is characterized by: The aerobic stabilization endpoints of each pollutant in the garbage are: The aerobic stabilization endpoint threshold of (cellulose + hemicellulose) / lignin ((C+H) / L) is 0.2; The aerobic stabilization endpoint threshold of biodegradability (BDM) is 3%; The aerobic stabilization endpoint threshold of the chemical oxygen demand (COD) of the leachate is 100 mg / L; The aerobic stabilization endpoint threshold of ammonia nitrogen is 25 mg / L.

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