A method for coupling treatment of excess sludge

Abstract

The present invention discloses a method for coupling treatment of excess sludge, belonging to the technical field of excess sludge treatment, and solves the problem that the existing method for treating excess sludge based on ultrasonic coupling with alkali restricts the sludge treatment efficiency because the sludge activity is not maximally guaranteed. By establishing the mathematical relationship between the carbon source release amount, the specific aerobic rate and the operating parameters, the present invention realizes the dynamic coupling optimization among the parameters, and based on multi-objective optimization, not only further reduces the ultrasonic energy consumption, but also obtains the optimal pH value, that is, the optimal solution for simultaneously increasing the carbon source release amount and the sludge activity. For subsequent in-situ resource utilization of sludge, it not only reduces the sludge production rate, but also improves the treatment efficiency of the biochemical system.

Description

Technical Field

[0001] The present invention relates to the technical field of excess sludge treatment, and particularly relates to a method for coupling treatment of excess sludge. Background Art

[0002] Currently, common methods for cracking excess sludge include oxidation method, alkali treatment method, ultrasonic method, heat treatment method, etc. Physical treatment methods based on heat, microwave and ultrasound have high energy consumption. Acid-base treatment, chemical oxidation and other methods have high chemical consumption, are easy to corrode equipment, have high carbon emissions and may cause secondary pollution. The treatment method using lysozyme has high cost and its stability remains to be verified. Among these methods, ultrasonic technology has been applied in actual projects. This technology realizes effective cracking of sludge through cavitation effect, promotes the release of organic matter to supplement carbon source for utilization, and creates conditions for the next step of utilization. However, ultrasonic has high power during the treatment process, often requires a very high energy density to be input, has the characteristics of high operating energy consumption and short service life of the device, which greatly limits its further popularization and application.

[0003] To solve this problem, the prior art usually uses an alkaline environment to improve the cell wall breaking efficiency of ultrasonic waves, thereby improving the utilization rate of ultrasonic waves. However, the prior art does not consider the relationship between ultrasonic density, pH value of the alkaline environment, carbon source release amount and sludge activity. Usually, the pH value is only roughly maintained at a certain relatively high value. For example, the invention patent with the publication number CN111646663B discloses a process for cracking sludge by hydrodynamic cavitation, which adjusts the pH value to 11 or 12. Although it improves the utilization rate of ultrasonic waves, promotes the release of carbon source, and to a certain extent ensures the activity of sludge, due to the rough setting of both the pH value and the ultrasonic energy consumption value, it does not optimize to improve the sludge activity, thus limiting the treatment efficiency of excess sludge. Summary of the Invention

[0004] Aiming at the above problems in the prior art, the present invention provides a method for coupling treatment of excess sludge, which solves the problem that the existing method for treating excess sludge based on ultrasonic coupling alkali limits the sludge treatment efficiency because the sludge activity is not maximally guaranteed.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] Provide a method for coupling treatment of excess sludge, including the steps:

[0007] S1, obtain the relational expression among the carbon source release amount, specific aerobic rate, pH value and ultrasonic energy density in the excess sludge;

[0008] S2. Determine the threshold of carbon source release amount according to the carbon source demand of the excess sludge, and constrain the carbon source release amount to be greater than this threshold. Establish an objective function for maximizing the specific aerobic rate while minimizing the ultrasonic energy density according to the relational expression, and solve the maximum value of the objective function to obtain the optimal pH value and the optimal ultrasonic energy density value;

[0009] S3. Synchronously perform coupling treatment on the excess sludge according to the optimal pH value and the optimal ultrasonic energy density value.

[0010] In this solution, by establishing the mathematical relationships among the carbon source release amount, the specific aerobic rate, and the operating parameters, the dynamic coupling optimization among the parameters is realized, and the optimal pH value is obtained based on multi-objective optimization, so as to maximize the sludge activity and minimize the ultrasonic energy density. On the premise of ensuring the carbon source release demand, not only the sludge production rate is reduced, but also the energy utilization efficiency and the sludge treatment efficiency are significantly improved.

[0011] Further, the relational expression in step S1 is:

[0012]

[0013] SOUR=-129.78+89.22·b-2147.88·b 2 +18632.61·b 3 -68286.24·b 4

[0014] +89519.73·b 5 -14.02·ln(10 -a )-0.33·[ln(10 -a )] 2

[0015] where, S COD is the carbon source release amount; SOUR is the specific aerobic rate; a is the pH value, and b is the ultrasonic energy density.

[0016] In this solution, 10 -ais the concentration of hydrogen ions, which can be directly obtained by measuring the concentration of hydrogen ions, and is more accurate. The polynomial logarithmic mixing equation structure can accurately characterize the exponential decay characteristics of SOUR at a given pH value, reducing the prediction error compared to the linear model. SOUR represents the utilization efficiency of dissolved oxygen by microorganisms in sludge and can be used to characterize sludge activity. The greater the SOUR, the higher the sludge activity. This relationship shows that when the pH is less than 10, alkali stimulates cells to secrete more extracellular polymers, and SOUR gradually increases. When the pH is greater than 10, the dissolution of extracellular polymers by alkali is further aggravated, even leading to cell lysis, thereby releasing more organic matter. At this time, SOUR shows a slight decrease, but compared with the untreated excess sludge, the activity is still in an enhanced state. SOUR first increases and then decreases with the increase of ultrasonic energy density, indicating that low-density ultrasound can not only promote the release of organic matter in sludge but also enhance sludge activity. The relationship shows that under milder alkaline environmental conditions, excess sludge can simultaneously achieve the release of COD and the improvement of the activity of treated sludge, solving the problem that the release of intracellular carbon sources during the sludge crushing process is accompanied by a decrease in sludge activity.

[0017] Further, the objective function C in step S2 is: C = w1SOUR - w2·b, where w1 and w2 are the weights of SOUR and b respectively. The setting of the weights can be selected according to the actual situation, focusing on either sludge treatment efficiency or ultrasonic energy consumption, which is more in line with the actual production needs.

[0018] Further, the solution method for step S2 is: construct the Lagrangian function and determine the constraint conditions, and combine the boundary conditions to obtain the optimal pH value and the optimal ultrasonic energy density value, where:

[0019]

[0020] the constraint conditions for are:

[0021]

[0022] where, is the Lagrangian function of pH value a, ultrasonic energy density b and Lagrange multiplier λ; SCOD min is the threshold.

[0023] In this solution, the rigid requirement of ensuring that the carbon source release amount is greater than the threshold is to avoid the risk of insufficient carbon source that may be caused by the traditional trial-and-error method.

[0024] Further, the boundary conditions of the Lagrangian function also include: the range of ultrasonic energy density b is 0 - 0.1 W / mL. Narrowing the ultrasonic range of low-density ultrasound further reduces the ultrasonic energy consumption.

[0025] Furthermore, the boundary conditions of the Lagrangian function also include: the range of pH value a is 9-11, avoiding extreme pH conditions.

[0026] The present invention discloses a method for coupling treatment of excess sludge, and its beneficial effects are as follows:

[0027] 1. By establishing the mathematical relationships among the carbon source release amount, specific aerobic rate and operating parameters, the present invention realizes the dynamic coupling optimization among the parameters. Based on the multi-objective optimization method, not only the ultrasonic energy consumption is further reduced, but also the optimal pH value is obtained, that is, the optimal solution for simultaneously increasing the carbon source release amount and sludge activity is obtained. For the subsequent in-situ resource utilization of sludge, it not only reduces the sludge production rate, but also improves the treatment efficiency of the biochemical system.

[0028] 2. The relational expression of the present invention shows that under milder alkaline environmental conditions, when the pH value is less than 11 and close to 10, the excess sludge can simultaneously achieve COD release and improvement of the activity of the treated sludge, solving the problem that the release of intracellular carbon source during the sludge crushing process is accompanied by a decrease in sludge activity in the past. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic structural diagram of the method for coupling treatment of excess sludge. DETAILED DESCRIPTION OF THE INVENTION

[0030] The following describes the specific embodiments of the present invention to facilitate those skilled in the art of the present technology to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art of the present technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

[0031] The prior art does not consider the relationship among ultrasonic density, pH value of the alkaline environment, carbon source release amount, and sludge activity. Usually, the pH value is only roughly maintained at a relatively high value, and is basically set at 11 or above. Although the utilization rate of ultrasonic waves is increased, the release of carbon source is promoted, and the activity of sludge is ensured to a certain extent, but since both the pH value and the ultrasonic energy consumption value are roughly set, there is no optimization to improve the sludge activity, thus limiting the treatment efficiency of excess sludge. To solve this problem, the present application provides a method for coupling treatment of excess sludge. By establishing the mathematical relationship among carbon source release amount, specific aerobic rate, and operating parameters, dynamic coupling optimization among parameters is realized, and the optimal solution for simultaneously increasing the carbon source release amount and sludge activity, that is, the optimal pH value, is obtained based on the multi-objective optimization method. This not only maximizes the treatment efficiency of the biochemical system, but also shows that the optimal pH value is less than 11, breaking the conventional pH value setting.

[0032] Reference Figure 1 , a method for coupling treatment of excess sludge, comprising the steps of:

[0033] S1. Obtain the relational expressions among carbon source release amount, specific aerobic rate, pH value, and ultrasonic energy density in the excess sludge.

[0034] The relational expressions in step S1 include:

[0035]

[0036] Among them, S COD is the carbon source release amount, which represents the relationship between the COD concentration in the sludge supernatant after treatment of the excess sludge and the ultrasonic energy density and pH in the low-density ultrasonic range, with the unit of mg / L; a is the pH value, and b is the ultrasonic energy density, with the range of 0 - 0.3 W / mL.

[0037] The COD concentration in the sludge supernatant after treatment first increases and then gradually levels off as the ultrasonic energy density increases, and the greater the pH, the greater the slope of the increasing trend of the COD concentration as the ultrasonic energy density increases. Therefore, the range of ultrasonic energy density can be reduced to (0 - 0.1 W / mL), further reducing the ultrasonic energy density, thereby reducing the ultrasonic energy consumption. In addition, the stimulation of lower pH (9 - 11) and low-density ultrasonic waves can not only release the organic matter in the sludge flocs, but also improve the activity of the sludge. The relationship between the specific aerobic rate (SOUR) of the sludge after treatment and ultrasonic and pH is as follows:

[0038] SOUR = -129.78 + 89.22·b - 2147.88·b 2 + 18632.61·b 3 - 68286.24·b 4

[0039] +89519.73·b 5 -14.02·ln(10 -a )-0.33·[ln(10 -a )] 2

[0040] Among them, SOUR is the specific aerobic rate, and the unit is mgO2 / gSS·h. This relational expression indicates that when the pH is less than 10, alkali stimulates cells to secrete more extracellular polymers, and SOUR gradually increases. When the pH is greater than 10, the dissolution of extracellular polymers by alkali is further aggravated, even cell lysis occurs, thereby releasing more organic matter. However, at this time, SOUR shows a slight decrease, but compared with the untreated excess sludge, the activity is still in an enhanced state. SOUR first increases and then decreases with the increase of ultrasonic energy density, which means that low-density ultrasonic wave can not only promote the release of organic matter in sludge, but also enhance the sludge activity.

[0041] S2. Determine the threshold of the carbon source release amount according to the carbon source demand of the excess sludge, and constrain the carbon source release amount to be greater than this threshold. Establish an objective function for maximizing the specific aerobic rate and minimizing the ultrasonic energy density according to the relational expression, and solve the maximum value of the objective function to obtain the optimal pH value and the optimal ultrasonic energy density value.

[0042] The objective function C of step S2 is: C = w1SOUR - w2·b, where w1 and w2 are the weights of SOUR and b respectively. The setting of the weights can be selected according to the actual situation whether to focus on the sludge treatment efficiency or the ultrasonic energy consumption, which is more in line with the actual production needs.

[0043] The solution method of step S2 can be a genetic algorithm or a multi-objective optimization algorithm. Specifically, in this solution, a Lagrangian function is constructed and the constraint conditions are determined, and the optimal pH value and the optimal ultrasonic energy density value are obtained in combination with the boundary conditions, where:

[0044]

[0045] The expressions of the constraint conditions and boundary conditions of

[0046]

[0047] are: is the Lagrangian function of the pH value a, the ultrasonic energy density b and the Lagrange multiplier λ; SCOD min is the threshold.

[0048] S3. Synchronously perform coupling treatment on the excess sludge according to the optimal pH value and the optimal ultrasonic energy density value.

[0049] Although the specific embodiments of the invention have been described in detail with reference to the accompanying drawings, it should not be construed as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative efforts still fall within the scope of protection of this patent.

Claims

1. A method for coupling treatment of excess sludge, characterized in that, Including the steps: S1. Obtain the relationship between the carbon source release amount, specific aerobic rate, pH value and ultrasonic energy density in the excess sludge; The relationship in step S1 is: Among them, is the carbon source release amount; is the specific aerobic rate; is the pH value, is the ultrasonic energy density; S2. Determine the threshold value of the carbon source release amount according to the carbon source demand of the excess sludge, and constrain the carbon source release amount to be greater than this threshold value. Establish an objective function for maximizing the specific aerobic rate and minimizing the ultrasonic energy density according to the relationship, and solve the maximum value of the objective function to obtain the optimal pH value and the optimal ultrasonic energy density value; The objective function of step S2 is as follows: , where and are respectively and the weights of The solution method for step S2 is: construct a Lagrangian function and determine constraint conditions, and combine boundary conditions to obtain the optimal pH value and the optimal ultrasonic energy density value, where: The constraint conditions are as follows: Among them, is the pH value , the ultrasonic energy density and the Lagrange multiplier of the Lagrangian function; is the threshold; S3. Synchronously perform coupling treatment on the excess sludge according to the optimal pH value and the optimal ultrasonic energy density value.

2. The method for coupling treatment of excess sludge according to claim 1, characterized in that Lagrange function The boundary conditions of include that the range of ultrasonic energy density is 0~0.1 W / mL.

3. The method for co-processing of excess sludge according to claim 2, wherein Lagrangian function The boundary conditions of include: the pH value ranges from 9 to 11.

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